chrome/browser/sessions/session

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This source file includes following definitions.
AdjustShowState
MigrateClosedPayload
force_browser_not_alive_with_no_windows_
force_browser_not_alive_with_no_windows_
RestoreIfNecessary
ResetFromCurrentBrowsers
MoveCurrentSessionToLastSession
SetTabWindow
SetWindowBounds
SetTabIndexInWindow
SetPinnedState
TabClosed
WindowOpened
WindowClosing
WindowClosed
SetWindowType
SetWindowAppName
TabNavigationPathPrunedFromBack
TabNavigationPathPrunedFromFront
UpdateTabNavigation
TabRestored
SetSelectedNavigationIndex
SetSelectedTabInWindow
SetTabUserAgentOverride
GetLastSession
Save
Init
processed_any_commands
ShouldNewWindowStartSession
RestoreIfNecessary
Observe
OnBrowserSetLastActive
SetTabExtensionAppID
CreateSetSelectedTabInWindow
CreateSetTabWindowCommand
CreateSetWindowBoundsCommand
CreateSetTabIndexInWindowCommand
CreateTabClosedCommand
CreateWindowClosedCommand
CreateSetSelectedNavigationIndexCommand
CreateSetWindowTypeCommand
CreatePinnedStateCommand
CreateSessionStorageAssociatedCommand
CreateSetActiveWindowCommand
OnGotSessionCommands
RestoreSessionFromCommands
UpdateSelectedTabIndex
GetWindow
GetTab
FindClosestNavigationWithIndex
WindowOrderSortFunction
TabVisualIndexSortFunction
SortTabsBasedOnVisualOrderAndPrune
AddTabsToWindows
CreateTabsAndWindows
BuildCommandsForTab
BuildCommandsForBrowser
BuildCommandsFromBrowsers
ScheduleReset
ReplacePendingCommand
ScheduleCommand
CommitPendingCloses
IsOnlyOneTabLeft
HasOpenTrackableBrowsers
ShouldTrackChangesToWindow
ShouldTrackBrowser
should_track_changes_for_browser_type
WindowTypeForBrowserType
BrowserTypeForWindowType
RecordSessionUpdateHistogramData
RecordUpdatedTabClosed
RecordUpdatedNavListPruned
RecordUpdatedNavEntryCommit
RecordUpdatedSessionNavigationOrTab
RecordUpdatedSaveTime
TabInserted
TabClosing
MaybeDeleteSessionOnlyData
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/sessions/session_service.h"

#include <algorithm>
#include <set>
#include <utility>
#include <vector>

#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/command_line.h"
#include "base/message_loop/message_loop.h"
#include "base/metrics/histogram.h"
#include "base/pickle.h"
#include "base/threading/thread.h"
#include "chrome/browser/background/background_mode_manager.h"
#include "chrome/browser/browser_process.h"
#include "chrome/browser/chrome_notification_types.h"
#include "chrome/browser/defaults.h"
#include "chrome/browser/extensions/tab_helper.h"
#include "chrome/browser/prefs/session_startup_pref.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/browser/profiles/profile_manager.h"
#include "chrome/browser/sessions/session_backend.h"
#include "chrome/browser/sessions/session_command.h"
#include "chrome/browser/sessions/session_data_deleter.h"
#include "chrome/browser/sessions/session_restore.h"
#include "chrome/browser/sessions/session_tab_helper.h"
#include "chrome/browser/sessions/session_types.h"
#include "chrome/browser/ui/browser_iterator.h"
#include "chrome/browser/ui/browser_list.h"
#include "chrome/browser/ui/browser_tabstrip.h"
#include "chrome/browser/ui/browser_window.h"
#include "chrome/browser/ui/host_desktop.h"
#include "chrome/browser/ui/startup/startup_browser_creator.h"
#include "chrome/browser/ui/tabs/tab_strip_model.h"
#include "components/startup_metric_utils/startup_metric_utils.h"
#include "content/public/browser/navigation_details.h"
#include "content/public/browser/navigation_entry.h"
#include "content/public/browser/notification_details.h"
#include "content/public/browser/notification_service.h"
#include "content/public/browser/session_storage_namespace.h"
#include "content/public/browser/web_contents.h"
#include "extensions/common/extension.h"

#if defined(OS_MACOSX)
#include "chrome/browser/app_controller_mac.h"
#endif

using base::Time;
using content::NavigationEntry;
using content::WebContents;
using sessions::SerializedNavigationEntry;

// Identifier for commands written to file.
static const SessionCommand::id_type kCommandSetTabWindow = 0;
// OBSOLETE Superseded by kCommandSetWindowBounds3.
// static const SessionCommand::id_type kCommandSetWindowBounds = 1;
static const SessionCommand::id_type kCommandSetTabIndexInWindow = 2;
// Original kCommandTabClosed/kCommandWindowClosed. See comment in
// MigrateClosedPayload for details on why they were replaced.
static const SessionCommand::id_type kCommandTabClosedObsolete = 3;
static const SessionCommand::id_type kCommandWindowClosedObsolete = 4;
static const SessionCommand::id_type
    kCommandTabNavigationPathPrunedFromBack = 5;
static const SessionCommand::id_type kCommandUpdateTabNavigation = 6;
static const SessionCommand::id_type kCommandSetSelectedNavigationIndex = 7;
static const SessionCommand::id_type kCommandSetSelectedTabInIndex = 8;
static const SessionCommand::id_type kCommandSetWindowType = 9;
// OBSOLETE Superseded by kCommandSetWindowBounds3. Except for data migration.
// static const SessionCommand::id_type kCommandSetWindowBounds2 = 10;
static const SessionCommand::id_type
    kCommandTabNavigationPathPrunedFromFront = 11;
static const SessionCommand::id_type kCommandSetPinnedState = 12;
static const SessionCommand::id_type kCommandSetExtensionAppID = 13;
static const SessionCommand::id_type kCommandSetWindowBounds3 = 14;
static const SessionCommand::id_type kCommandSetWindowAppName = 15;
static const SessionCommand::id_type kCommandTabClosed = 16;
static const SessionCommand::id_type kCommandWindowClosed = 17;
static const SessionCommand::id_type kCommandSetTabUserAgentOverride = 18;
static const SessionCommand::id_type kCommandSessionStorageAssociated = 19;
static const SessionCommand::id_type kCommandSetActiveWindow = 20;

// Every kWritesPerReset commands triggers recreating the file.
static const int kWritesPerReset = 250;

namespace {

// Various payload structures.
struct ClosedPayload {
  SessionID::id_type id;
  int64 close_time;
};

struct WindowBoundsPayload2 {
  SessionID::id_type window_id;
  int32 x;
  int32 y;
  int32 w;
  int32 h;
  bool is_maximized;
};

struct WindowBoundsPayload3 {
  SessionID::id_type window_id;
  int32 x;
  int32 y;
  int32 w;
  int32 h;
  int32 show_state;
};

typedef SessionID::id_type ActiveWindowPayload;

struct IDAndIndexPayload {
  SessionID::id_type id;
  int32 index;
};

typedef IDAndIndexPayload TabIndexInWindowPayload;

typedef IDAndIndexPayload TabNavigationPathPrunedFromBackPayload;

typedef IDAndIndexPayload SelectedNavigationIndexPayload;

typedef IDAndIndexPayload SelectedTabInIndexPayload;

typedef IDAndIndexPayload WindowTypePayload;

typedef IDAndIndexPayload TabNavigationPathPrunedFromFrontPayload;

struct PinnedStatePayload {
  SessionID::id_type tab_id;
  bool pinned_state;
};

// Returns the show state to store to disk based |state|.
ui::WindowShowState AdjustShowState(ui::WindowShowState state) {
  switch (state) {
    case ui::SHOW_STATE_NORMAL:
    case ui::SHOW_STATE_MINIMIZED:
    case ui::SHOW_STATE_MAXIMIZED:
    case ui::SHOW_STATE_FULLSCREEN:
    case ui::SHOW_STATE_DETACHED:
      return state;

    case ui::SHOW_STATE_DEFAULT:
    case ui::SHOW_STATE_INACTIVE:
    case ui::SHOW_STATE_END:
      return ui::SHOW_STATE_NORMAL;
  }
  return ui::SHOW_STATE_NORMAL;
}

// Migrates a |ClosedPayload|, returning true on success (migration was
// necessary and happened), or false (migration was not necessary or was not
// successful).
bool MigrateClosedPayload(const SessionCommand& command,
                          ClosedPayload* payload) {
#if defined(OS_CHROMEOS)
  // Pre M17 versions of chromeos were 32bit. Post M17 is 64 bit. Apparently the
  // 32 bit versions of chrome on pre M17 resulted in a sizeof 12 for the
  // ClosedPayload, where as post M17 64-bit gives a sizeof 16 (presumably the
  // struct is padded).
  if ((command.id() == kCommandWindowClosedObsolete ||
       command.id() == kCommandTabClosedObsolete) &&
      command.size() == 12 && sizeof(payload->id) == 4 &&
      sizeof(payload->close_time) == 8) {
    memcpy(&payload->id, command.contents(), 4);
    memcpy(&payload->close_time, command.contents() + 4, 8);
    return true;
  } else {
    return false;
  }
#else
  return false;
#endif
}

}  // namespace

// SessionService -------------------------------------------------------------

SessionService::SessionService(Profile* profile)
    : BaseSessionService(SESSION_RESTORE, profile, base::FilePath()),
      has_open_trackable_browsers_(false),
      move_on_new_browser_(false),
      save_delay_in_millis_(base::TimeDelta::FromMilliseconds(2500)),
      save_delay_in_mins_(base::TimeDelta::FromMinutes(10)),
      save_delay_in_hrs_(base::TimeDelta::FromHours(8)),
      force_browser_not_alive_with_no_windows_(false) {
  Init();
}

SessionService::SessionService(const base::FilePath& save_path)
    : BaseSessionService(SESSION_RESTORE, NULL, save_path),
      has_open_trackable_browsers_(false),
      move_on_new_browser_(false),
      save_delay_in_millis_(base::TimeDelta::FromMilliseconds(2500)),
      save_delay_in_mins_(base::TimeDelta::FromMinutes(10)),
      save_delay_in_hrs_(base::TimeDelta::FromHours(8)),
      force_browser_not_alive_with_no_windows_(false)  {
  Init();
}

SessionService::~SessionService() {
  // The BrowserList should outlive the SessionService since it's static and
  // the SessionService is a KeyedService.
  BrowserList::RemoveObserver(this);
  Save();
}

bool SessionService::RestoreIfNecessary(const std::vector<GURL>& urls_to_open) {
  return RestoreIfNecessary(urls_to_open, NULL);
}

void SessionService::ResetFromCurrentBrowsers() {
  ScheduleReset();
}

void SessionService::MoveCurrentSessionToLastSession() {
  pending_tab_close_ids_.clear();
  window_closing_ids_.clear();
  pending_window_close_ids_.clear();

  Save();

  RunTaskOnBackendThread(
      FROM_HERE, base::Bind(&SessionBackend::MoveCurrentSessionToLastSession,
                            backend()));
}

void SessionService::SetTabWindow(const SessionID& window_id,
                                  const SessionID& tab_id) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreateSetTabWindowCommand(window_id, tab_id));
}

void SessionService::SetWindowBounds(const SessionID& window_id,
                                     const gfx::Rect& bounds,
                                     ui::WindowShowState show_state) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreateSetWindowBoundsCommand(window_id, bounds, show_state));
}

void SessionService::SetTabIndexInWindow(const SessionID& window_id,
                                         const SessionID& tab_id,
                                         int new_index) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreateSetTabIndexInWindowCommand(tab_id, new_index));
}

void SessionService::SetPinnedState(const SessionID& window_id,
                                    const SessionID& tab_id,
                                    bool is_pinned) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreatePinnedStateCommand(tab_id, is_pinned));
}

void SessionService::TabClosed(const SessionID& window_id,
                               const SessionID& tab_id,
                               bool closed_by_user_gesture) {
  if (!tab_id.id())
    return;  // Hapens when the tab is replaced.

  if (!ShouldTrackChangesToWindow(window_id))
    return;

  IdToRange::iterator i = tab_to_available_range_.find(tab_id.id());
  if (i != tab_to_available_range_.end())
    tab_to_available_range_.erase(i);

  if (find(pending_window_close_ids_.begin(), pending_window_close_ids_.end(),
           window_id.id()) != pending_window_close_ids_.end()) {
    // Tab is in last window. Don't commit it immediately, instead add it to the
    // list of tabs to close. If the user creates another window, the close is
    // committed.
    pending_tab_close_ids_.insert(tab_id.id());
  } else if (find(window_closing_ids_.begin(), window_closing_ids_.end(),
                  window_id.id()) != window_closing_ids_.end() ||
             !IsOnlyOneTabLeft() ||
             closed_by_user_gesture) {
    // Close is the result of one of the following:
    // . window close (and it isn't the last window).
    // . closing a tab and there are other windows/tabs open.
    // . closed by a user gesture.
    // In all cases we need to mark the tab as explicitly closed.
    ScheduleCommand(CreateTabClosedCommand(tab_id.id()));
  } else {
    // User closed the last tab in the last tabbed browser. Don't mark the
    // tab closed.
    pending_tab_close_ids_.insert(tab_id.id());
    has_open_trackable_browsers_ = false;
  }
}

void SessionService::WindowOpened(Browser* browser) {
  if (!ShouldTrackBrowser(browser))
    return;

  AppType app_type = browser->is_app() ? TYPE_APP : TYPE_NORMAL;
  RestoreIfNecessary(std::vector<GURL>(), browser);
  SetWindowType(browser->session_id(), browser->type(), app_type);
  SetWindowAppName(browser->session_id(), browser->app_name());
}

void SessionService::WindowClosing(const SessionID& window_id) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  // The window is about to close. If there are other tabbed browsers with the
  // same original profile commit the close immediately.
  //
  // NOTE: if the user chooses the exit menu item session service is destroyed
  // and this code isn't hit.
  if (has_open_trackable_browsers_) {
    // Closing a window can never make has_open_trackable_browsers_ go from
    // false to true, so only update it if already true.
    has_open_trackable_browsers_ = HasOpenTrackableBrowsers(window_id);
  }
  bool use_pending_close = !has_open_trackable_browsers_;
  if (!use_pending_close) {
    // Somewhat outside of "normal behavior" is profile locking.  In this case
    // (when IsSiginRequired has already been set True), we're closing all
    // browser windows in turn but want them all to be restored when the user
    // unlocks.  To accomplish this, we do a "pending close" on all windows
    // instead of just the last one (which has no open_trackable_browsers).
    // http://crbug.com/356818
    //
    // Some editions (like iOS) don't have a profile_manager and some tests
    // don't supply one so be lenient.
    if (g_browser_process) {
      ProfileManager* profile_manager = g_browser_process->profile_manager();
      if (profile_manager) {
        ProfileInfoCache& profile_info =
            profile_manager->GetProfileInfoCache();
        size_t profile_index = profile_info.GetIndexOfProfileWithPath(
            profile()->GetPath());
        use_pending_close = profile_index != std::string::npos &&
            profile_info.ProfileIsSigninRequiredAtIndex(profile_index);
      }
    }
  }
  if (use_pending_close)
    pending_window_close_ids_.insert(window_id.id());
  else
    window_closing_ids_.insert(window_id.id());
}

void SessionService::WindowClosed(const SessionID& window_id) {
  if (!ShouldTrackChangesToWindow(window_id)) {
    // The last window may be one that is not tracked.
    MaybeDeleteSessionOnlyData();
    return;
  }

  windows_tracking_.erase(window_id.id());

  if (window_closing_ids_.find(window_id.id()) != window_closing_ids_.end()) {
    window_closing_ids_.erase(window_id.id());
    ScheduleCommand(CreateWindowClosedCommand(window_id.id()));
  } else if (pending_window_close_ids_.find(window_id.id()) ==
             pending_window_close_ids_.end()) {
    // We'll hit this if user closed the last tab in a window.
    has_open_trackable_browsers_ = HasOpenTrackableBrowsers(window_id);
    if (!has_open_trackable_browsers_)
      pending_window_close_ids_.insert(window_id.id());
    else
      ScheduleCommand(CreateWindowClosedCommand(window_id.id()));
  }
  MaybeDeleteSessionOnlyData();
}

void SessionService::SetWindowType(const SessionID& window_id,
                                   Browser::Type type,
                                   AppType app_type) {
  if (!should_track_changes_for_browser_type(type, app_type))
    return;

  windows_tracking_.insert(window_id.id());

  // The user created a new tabbed browser with our profile. Commit any
  // pending closes.
  CommitPendingCloses();

  has_open_trackable_browsers_ = true;
  move_on_new_browser_ = true;

  ScheduleCommand(
      CreateSetWindowTypeCommand(window_id, WindowTypeForBrowserType(type)));
}

void SessionService::SetWindowAppName(
    const SessionID& window_id,
    const std::string& app_name) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreateSetTabExtensionAppIDCommand(
                      kCommandSetWindowAppName,
                      window_id.id(),
                      app_name));
}

void SessionService::TabNavigationPathPrunedFromBack(const SessionID& window_id,
                                                     const SessionID& tab_id,
                                                     int count) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  TabNavigationPathPrunedFromBackPayload payload = { 0 };
  payload.id = tab_id.id();
  payload.index = count;
  SessionCommand* command =
      new SessionCommand(kCommandTabNavigationPathPrunedFromBack,
                         sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  ScheduleCommand(command);
}

void SessionService::TabNavigationPathPrunedFromFront(
    const SessionID& window_id,
    const SessionID& tab_id,
    int count) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  // Update the range of indices.
  if (tab_to_available_range_.find(tab_id.id()) !=
      tab_to_available_range_.end()) {
    std::pair<int, int>& range = tab_to_available_range_[tab_id.id()];
    range.first = std::max(0, range.first - count);
    range.second = std::max(0, range.second - count);
  }

  TabNavigationPathPrunedFromFrontPayload payload = { 0 };
  payload.id = tab_id.id();
  payload.index = count;
  SessionCommand* command =
      new SessionCommand(kCommandTabNavigationPathPrunedFromFront,
                         sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  ScheduleCommand(command);
}

void SessionService::UpdateTabNavigation(
    const SessionID& window_id,
    const SessionID& tab_id,
    const SerializedNavigationEntry& navigation) {
  if (!ShouldTrackEntry(navigation.virtual_url()) ||
      !ShouldTrackChangesToWindow(window_id)) {
    return;
  }

  if (tab_to_available_range_.find(tab_id.id()) !=
      tab_to_available_range_.end()) {
    std::pair<int, int>& range = tab_to_available_range_[tab_id.id()];
    range.first = std::min(navigation.index(), range.first);
    range.second = std::max(navigation.index(), range.second);
  }
  ScheduleCommand(CreateUpdateTabNavigationCommand(kCommandUpdateTabNavigation,
                                                   tab_id.id(), navigation));
}

void SessionService::TabRestored(WebContents* tab, bool pinned) {
  SessionTabHelper* session_tab_helper = SessionTabHelper::FromWebContents(tab);
  if (!ShouldTrackChangesToWindow(session_tab_helper->window_id()))
    return;

  BuildCommandsForTab(session_tab_helper->window_id(), tab, -1,
                      pinned, &pending_commands(), NULL);
  StartSaveTimer();
}

void SessionService::SetSelectedNavigationIndex(const SessionID& window_id,
                                                const SessionID& tab_id,
                                                int index) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  if (tab_to_available_range_.find(tab_id.id()) !=
      tab_to_available_range_.end()) {
    if (index < tab_to_available_range_[tab_id.id()].first ||
        index > tab_to_available_range_[tab_id.id()].second) {
      // The new index is outside the range of what we've archived, schedule
      // a reset.
      ResetFromCurrentBrowsers();
      return;
    }
  }
  ScheduleCommand(CreateSetSelectedNavigationIndexCommand(tab_id, index));
}

void SessionService::SetSelectedTabInWindow(const SessionID& window_id,
                                            int index) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreateSetSelectedTabInWindow(window_id, index));
}

void SessionService::SetTabUserAgentOverride(
    const SessionID& window_id,
    const SessionID& tab_id,
    const std::string& user_agent_override) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreateSetTabUserAgentOverrideCommand(
      kCommandSetTabUserAgentOverride, tab_id.id(), user_agent_override));
}

base::CancelableTaskTracker::TaskId SessionService::GetLastSession(
    const SessionCallback& callback,
    base::CancelableTaskTracker* tracker) {
  // OnGotSessionCommands maps the SessionCommands to browser state, then run
  // the callback.
  return ScheduleGetLastSessionCommands(
      base::Bind(&SessionService::OnGotSessionCommands,
                 base::Unretained(this), callback),
      tracker);
}

void SessionService::Save() {
  bool had_commands = !pending_commands().empty();
  BaseSessionService::Save();
  if (had_commands) {
    RecordSessionUpdateHistogramData(chrome::NOTIFICATION_SESSION_SERVICE_SAVED,
                                     &last_updated_save_time_);
    content::NotificationService::current()->Notify(
        chrome::NOTIFICATION_SESSION_SERVICE_SAVED,
        content::Source<Profile>(profile()),
        content::NotificationService::NoDetails());
  }
}

void SessionService::Init() {
  // Register for the notifications we're interested in.
  registrar_.Add(this, content::NOTIFICATION_NAV_LIST_PRUNED,
                 content::NotificationService::AllSources());
  registrar_.Add(this, content::NOTIFICATION_NAV_ENTRY_CHANGED,
                 content::NotificationService::AllSources());
  registrar_.Add(this, content::NOTIFICATION_NAV_ENTRY_COMMITTED,
                 content::NotificationService::AllSources());
  registrar_.Add(
      this, chrome::NOTIFICATION_TAB_CONTENTS_APPLICATION_EXTENSION_CHANGED,
      content::NotificationService::AllSources());

  BrowserList::AddObserver(this);
}

bool SessionService::processed_any_commands() {
  return backend()->inited() || !pending_commands().empty();
}

bool SessionService::ShouldNewWindowStartSession() {
  // ChromeOS and OSX have different ideas of application lifetime than
  // the other platforms.
  // On ChromeOS opening a new window should never start a new session.
#if defined(OS_CHROMEOS)
  if (!force_browser_not_alive_with_no_windows_)
    return false;
#endif
  if (!has_open_trackable_browsers_ &&
      !StartupBrowserCreator::InSynchronousProfileLaunch() &&
      !SessionRestore::IsRestoring(profile())
#if defined(OS_MACOSX)
      // On OSX, a new window should not start a new session if it was opened
      // from the dock or the menubar.
      && !app_controller_mac::IsOpeningNewWindow()
#endif  // OS_MACOSX
      ) {
    return true;
  }
  return false;
}

bool SessionService::RestoreIfNecessary(const std::vector<GURL>& urls_to_open,
                                        Browser* browser) {
  if (ShouldNewWindowStartSession()) {
    // We're going from no tabbed browsers to a tabbed browser (and not in
    // process startup), restore the last session.
    if (move_on_new_browser_) {
      // Make the current session the last.
      MoveCurrentSessionToLastSession();
      move_on_new_browser_ = false;
    }
    SessionStartupPref pref = StartupBrowserCreator::GetSessionStartupPref(
        *CommandLine::ForCurrentProcess(), profile());
    if (pref.type == SessionStartupPref::LAST) {
      SessionRestore::RestoreSession(
          profile(), browser,
          browser ? browser->host_desktop_type() : chrome::GetActiveDesktop(),
          browser ? 0 : SessionRestore::ALWAYS_CREATE_TABBED_BROWSER,
          urls_to_open);
      return true;
    }
  }
  return false;
}

void SessionService::Observe(int type,
                             const content::NotificationSource& source,
                             const content::NotificationDetails& details) {
  // All of our messages have the NavigationController as the source.
  switch (type) {
    case content::NOTIFICATION_NAV_LIST_PRUNED: {
      WebContents* web_contents =
          content::Source<content::NavigationController>(source).ptr()->
              GetWebContents();
      SessionTabHelper* session_tab_helper =
          SessionTabHelper::FromWebContents(web_contents);
      if (!session_tab_helper || web_contents->GetBrowserContext() != profile())
        return;
      content::Details<content::PrunedDetails> pruned_details(details);
      if (pruned_details->from_front) {
        TabNavigationPathPrunedFromFront(
            session_tab_helper->window_id(),
            session_tab_helper->session_id(),
            pruned_details->count);
      } else {
        TabNavigationPathPrunedFromBack(
            session_tab_helper->window_id(),
            session_tab_helper->session_id(),
            web_contents->GetController().GetEntryCount());
      }
      RecordSessionUpdateHistogramData(type,
                                       &last_updated_nav_list_pruned_time_);
      break;
    }

    case content::NOTIFICATION_NAV_ENTRY_CHANGED: {
      WebContents* web_contents =
          content::Source<content::NavigationController>(source).ptr()->
              GetWebContents();
      SessionTabHelper* session_tab_helper =
          SessionTabHelper::FromWebContents(web_contents);
      if (!session_tab_helper || web_contents->GetBrowserContext() != profile())
        return;
      content::Details<content::EntryChangedDetails> changed(details);
      const SerializedNavigationEntry navigation =
          SerializedNavigationEntry::FromNavigationEntry(
              changed->index, *changed->changed_entry);
      UpdateTabNavigation(session_tab_helper->window_id(),
                          session_tab_helper->session_id(),
                          navigation);
      break;
    }

    case content::NOTIFICATION_NAV_ENTRY_COMMITTED: {
      WebContents* web_contents =
          content::Source<content::NavigationController>(source).ptr()->
              GetWebContents();
      SessionTabHelper* session_tab_helper =
          SessionTabHelper::FromWebContents(web_contents);
      if (!session_tab_helper || web_contents->GetBrowserContext() != profile())
        return;
      int current_entry_index =
          web_contents->GetController().GetCurrentEntryIndex();
      SetSelectedNavigationIndex(
          session_tab_helper->window_id(),
          session_tab_helper->session_id(),
          current_entry_index);
      const SerializedNavigationEntry navigation =
          SerializedNavigationEntry::FromNavigationEntry(
              current_entry_index,
              *web_contents->GetController().GetEntryAtIndex(
                  current_entry_index));
      UpdateTabNavigation(
          session_tab_helper->window_id(),
          session_tab_helper->session_id(),
          navigation);
      content::Details<content::LoadCommittedDetails> changed(details);
      if (changed->type == content::NAVIGATION_TYPE_NEW_PAGE ||
        changed->type == content::NAVIGATION_TYPE_EXISTING_PAGE) {
        RecordSessionUpdateHistogramData(type,
                                         &last_updated_nav_entry_commit_time_);
      }
      break;
    }

    case chrome::NOTIFICATION_TAB_CONTENTS_APPLICATION_EXTENSION_CHANGED: {
      extensions::TabHelper* extension_tab_helper =
          content::Source<extensions::TabHelper>(source).ptr();
      if (extension_tab_helper->web_contents()->GetBrowserContext() !=
              profile()) {
        return;
      }
      if (extension_tab_helper->extension_app()) {
        SessionTabHelper* session_tab_helper =
            SessionTabHelper::FromWebContents(
                extension_tab_helper->web_contents());
        SetTabExtensionAppID(session_tab_helper->window_id(),
                             session_tab_helper->session_id(),
                             extension_tab_helper->extension_app()->id());
      }
      break;
    }

    default:
      NOTREACHED();
  }
}

void SessionService::OnBrowserSetLastActive(Browser* browser) {
  if (ShouldTrackBrowser(browser))
    ScheduleCommand(CreateSetActiveWindowCommand(browser->session_id()));
}

void SessionService::SetTabExtensionAppID(
    const SessionID& window_id,
    const SessionID& tab_id,
    const std::string& extension_app_id) {
  if (!ShouldTrackChangesToWindow(window_id))
    return;

  ScheduleCommand(CreateSetTabExtensionAppIDCommand(kCommandSetExtensionAppID,
      tab_id.id(), extension_app_id));
}

SessionCommand* SessionService::CreateSetSelectedTabInWindow(
    const SessionID& window_id,
    int index) {
  SelectedTabInIndexPayload payload = { 0 };
  payload.id = window_id.id();
  payload.index = index;
  SessionCommand* command = new SessionCommand(kCommandSetSelectedTabInIndex,
                                 sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateSetTabWindowCommand(
    const SessionID& window_id,
    const SessionID& tab_id) {
  SessionID::id_type payload[] = { window_id.id(), tab_id.id() };
  SessionCommand* command =
      new SessionCommand(kCommandSetTabWindow, sizeof(payload));
  memcpy(command->contents(), payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateSetWindowBoundsCommand(
    const SessionID& window_id,
    const gfx::Rect& bounds,
    ui::WindowShowState show_state) {
  WindowBoundsPayload3 payload = { 0 };
  payload.window_id = window_id.id();
  payload.x = bounds.x();
  payload.y = bounds.y();
  payload.w = bounds.width();
  payload.h = bounds.height();
  payload.show_state = AdjustShowState(show_state);
  SessionCommand* command = new SessionCommand(kCommandSetWindowBounds3,
                                               sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateSetTabIndexInWindowCommand(
    const SessionID& tab_id,
    int new_index) {
  TabIndexInWindowPayload payload = { 0 };
  payload.id = tab_id.id();
  payload.index = new_index;
  SessionCommand* command =
      new SessionCommand(kCommandSetTabIndexInWindow, sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateTabClosedCommand(
    const SessionID::id_type tab_id) {
  ClosedPayload payload;
  // Because of what appears to be a compiler bug setting payload to {0} doesn't
  // set the padding to 0, resulting in Purify reporting an UMR when we write
  // the structure to disk. To avoid this we explicitly memset the struct.
  memset(&payload, 0, sizeof(payload));
  payload.id = tab_id;
  payload.close_time = Time::Now().ToInternalValue();
  SessionCommand* command =
      new SessionCommand(kCommandTabClosed, sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateWindowClosedCommand(
    const SessionID::id_type window_id) {
  ClosedPayload payload;
  // See comment in CreateTabClosedCommand as to why we do this.
  memset(&payload, 0, sizeof(payload));
  payload.id = window_id;
  payload.close_time = Time::Now().ToInternalValue();
  SessionCommand* command =
      new SessionCommand(kCommandWindowClosed, sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateSetSelectedNavigationIndexCommand(
    const SessionID& tab_id,
    int index) {
  SelectedNavigationIndexPayload payload = { 0 };
  payload.id = tab_id.id();
  payload.index = index;
  SessionCommand* command = new SessionCommand(
      kCommandSetSelectedNavigationIndex, sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateSetWindowTypeCommand(
    const SessionID& window_id,
    WindowType type) {
  WindowTypePayload payload = { 0 };
  payload.id = window_id.id();
  payload.index = static_cast<int32>(type);
  SessionCommand* command = new SessionCommand(
      kCommandSetWindowType, sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreatePinnedStateCommand(
    const SessionID& tab_id,
    bool is_pinned) {
  PinnedStatePayload payload = { 0 };
  payload.tab_id = tab_id.id();
  payload.pinned_state = is_pinned;
  SessionCommand* command =
      new SessionCommand(kCommandSetPinnedState, sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

SessionCommand* SessionService::CreateSessionStorageAssociatedCommand(
    const SessionID& tab_id,
    const std::string& session_storage_persistent_id) {
  Pickle pickle;
  pickle.WriteInt(tab_id.id());
  pickle.WriteString(session_storage_persistent_id);
  return new SessionCommand(kCommandSessionStorageAssociated, pickle);
}

SessionCommand* SessionService::CreateSetActiveWindowCommand(
    const SessionID& window_id) {
  ActiveWindowPayload payload = 0;
  payload = window_id.id();
  SessionCommand* command =
      new SessionCommand(kCommandSetActiveWindow, sizeof(payload));
  memcpy(command->contents(), &payload, sizeof(payload));
  return command;
}

void SessionService::OnGotSessionCommands(
    const SessionCallback& callback,
    ScopedVector<SessionCommand> commands) {
  ScopedVector<SessionWindow> valid_windows;
  SessionID::id_type active_window_id = 0;

  RestoreSessionFromCommands(
      commands.get(), &valid_windows.get(), &active_window_id);
  callback.Run(valid_windows.Pass(), active_window_id);
}

void SessionService::RestoreSessionFromCommands(
    const std::vector<SessionCommand*>& commands,
    std::vector<SessionWindow*>* valid_windows,
    SessionID::id_type* active_window_id) {
  std::map<int, SessionTab*> tabs;
  std::map<int, SessionWindow*> windows;

  VLOG(1) << "RestoreSessionFromCommands " << commands.size();
  if (CreateTabsAndWindows(commands, &tabs, &windows, active_window_id)) {
    AddTabsToWindows(&tabs, &windows);
    SortTabsBasedOnVisualOrderAndPrune(&windows, valid_windows);
    UpdateSelectedTabIndex(valid_windows);
  }
  STLDeleteValues(&tabs);
  // Don't delete conents of windows, that is done by the caller as all
  // valid windows are added to valid_windows.
}

void SessionService::UpdateSelectedTabIndex(
    std::vector<SessionWindow*>* windows) {
  for (std::vector<SessionWindow*>::const_iterator i = windows->begin();
       i != windows->end(); ++i) {
    // See note in SessionWindow as to why we do this.
    int new_index = 0;
    for (std::vector<SessionTab*>::const_iterator j = (*i)->tabs.begin();
         j != (*i)->tabs.end(); ++j) {
      if ((*j)->tab_visual_index == (*i)->selected_tab_index) {
        new_index = static_cast<int>(j - (*i)->tabs.begin());
        break;
      }
    }
    (*i)->selected_tab_index = new_index;
  }
}

SessionWindow* SessionService::GetWindow(
    SessionID::id_type window_id,
    IdToSessionWindow* windows) {
  std::map<int, SessionWindow*>::iterator i = windows->find(window_id);
  if (i == windows->end()) {
    SessionWindow* window = new SessionWindow();
    window->window_id.set_id(window_id);
    (*windows)[window_id] = window;
    return window;
  }
  return i->second;
}

SessionTab* SessionService::GetTab(
    SessionID::id_type tab_id,
    IdToSessionTab* tabs) {
  DCHECK(tabs);
  std::map<int, SessionTab*>::iterator i = tabs->find(tab_id);
  if (i == tabs->end()) {
    SessionTab* tab = new SessionTab();
    tab->tab_id.set_id(tab_id);
    (*tabs)[tab_id] = tab;
    return tab;
  }
  return i->second;
}

std::vector<SerializedNavigationEntry>::iterator
  SessionService::FindClosestNavigationWithIndex(
    std::vector<SerializedNavigationEntry>* navigations,
    int index) {
  DCHECK(navigations);
  for (std::vector<SerializedNavigationEntry>::iterator
           i = navigations->begin(); i != navigations->end(); ++i) {
    if (i->index() >= index)
      return i;
  }
  return navigations->end();
}

// Function used in sorting windows. Sorting is done based on window id. As
// window ids increment for each new window, this effectively sorts by creation
// time.
static bool WindowOrderSortFunction(const SessionWindow* w1,
                                    const SessionWindow* w2) {
  return w1->window_id.id() < w2->window_id.id();
}

// Compares the two tabs based on visual index.
static bool TabVisualIndexSortFunction(const SessionTab* t1,
                                       const SessionTab* t2) {
  const int delta = t1->tab_visual_index - t2->tab_visual_index;
  return delta == 0 ? (t1->tab_id.id() < t2->tab_id.id()) : (delta < 0);
}

void SessionService::SortTabsBasedOnVisualOrderAndPrune(
    std::map<int, SessionWindow*>* windows,
    std::vector<SessionWindow*>* valid_windows) {
  std::map<int, SessionWindow*>::iterator i = windows->begin();
  while (i != windows->end()) {
    SessionWindow* window = i->second;
    AppType app_type = window->app_name.empty() ? TYPE_NORMAL : TYPE_APP;
    if (window->tabs.empty() || window->is_constrained ||
        !should_track_changes_for_browser_type(
            static_cast<Browser::Type>(window->type),
            app_type)) {
      delete window;
      windows->erase(i++);
    } else {
      // Valid window; sort the tabs and add it to the list of valid windows.
      std::sort(window->tabs.begin(), window->tabs.end(),
                &TabVisualIndexSortFunction);
      // Otherwise, add the window such that older windows appear first.
      if (valid_windows->empty()) {
        valid_windows->push_back(window);
      } else {
        valid_windows->insert(
            std::upper_bound(valid_windows->begin(), valid_windows->end(),
                             window, &WindowOrderSortFunction),
            window);
      }
      ++i;
    }
  }
}

void SessionService::AddTabsToWindows(std::map<int, SessionTab*>* tabs,
                                      std::map<int, SessionWindow*>* windows) {
  VLOG(1) << "AddTabsToWindws";
  VLOG(1) << "Tabs " << tabs->size() << ", windows " << windows->size();
  std::map<int, SessionTab*>::iterator i = tabs->begin();
  while (i != tabs->end()) {
    SessionTab* tab = i->second;
    if (tab->window_id.id() && !tab->navigations.empty()) {
      SessionWindow* window = GetWindow(tab->window_id.id(), windows);
      window->tabs.push_back(tab);
      tabs->erase(i++);

      // See note in SessionTab as to why we do this.
      std::vector<SerializedNavigationEntry>::iterator j =
          FindClosestNavigationWithIndex(&(tab->navigations),
                                         tab->current_navigation_index);
      if (j == tab->navigations.end()) {
        tab->current_navigation_index =
            static_cast<int>(tab->navigations.size() - 1);
      } else {
        tab->current_navigation_index =
            static_cast<int>(j - tab->navigations.begin());
      }
    } else {
      // Never got a set tab index in window, or tabs are empty, nothing
      // to do.
      ++i;
    }
  }
}

bool SessionService::CreateTabsAndWindows(
    const std::vector<SessionCommand*>& data,
    std::map<int, SessionTab*>* tabs,
    std::map<int, SessionWindow*>* windows,
    SessionID::id_type* active_window_id) {
  // If the file is corrupt (command with wrong size, or unknown command), we
  // still return true and attempt to restore what we we can.
  VLOG(1) << "CreateTabsAndWindows";

  startup_metric_utils::ScopedSlowStartupUMA
      scoped_timer("Startup.SlowStartupSessionServiceCreateTabsAndWindows");

  for (std::vector<SessionCommand*>::const_iterator i = data.begin();
       i != data.end(); ++i) {
    const SessionCommand::id_type kCommandSetWindowBounds2 = 10;
    const SessionCommand* command = *i;

    VLOG(1) << "Read command " << (int) command->id();
    switch (command->id()) {
      case kCommandSetTabWindow: {
        SessionID::id_type payload[2];
        if (!command->GetPayload(payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetTab(payload[1], tabs)->window_id.set_id(payload[0]);
        break;
      }

      // This is here for forward migration only.  New data is saved with
      // |kCommandSetWindowBounds3|.
      case kCommandSetWindowBounds2: {
        WindowBoundsPayload2 payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetWindow(payload.window_id, windows)->bounds.SetRect(payload.x,
                                                              payload.y,
                                                              payload.w,
                                                              payload.h);
        GetWindow(payload.window_id, windows)->show_state =
            payload.is_maximized ?
                ui::SHOW_STATE_MAXIMIZED : ui::SHOW_STATE_NORMAL;
        break;
      }

      case kCommandSetWindowBounds3: {
        WindowBoundsPayload3 payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetWindow(payload.window_id, windows)->bounds.SetRect(payload.x,
                                                              payload.y,
                                                              payload.w,
                                                              payload.h);
        // SHOW_STATE_INACTIVE is not persisted.
        ui::WindowShowState show_state = ui::SHOW_STATE_NORMAL;
        if (payload.show_state > ui::SHOW_STATE_DEFAULT &&
            payload.show_state < ui::SHOW_STATE_END &&
            payload.show_state != ui::SHOW_STATE_INACTIVE) {
          show_state = static_cast<ui::WindowShowState>(payload.show_state);
        } else {
          NOTREACHED();
        }
        GetWindow(payload.window_id, windows)->show_state = show_state;
        break;
      }

      case kCommandSetTabIndexInWindow: {
        TabIndexInWindowPayload payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetTab(payload.id, tabs)->tab_visual_index = payload.index;
        break;
      }

      case kCommandTabClosedObsolete:
      case kCommandWindowClosedObsolete:
      case kCommandTabClosed:
      case kCommandWindowClosed: {
        ClosedPayload payload;
        if (!command->GetPayload(&payload, sizeof(payload)) &&
            !MigrateClosedPayload(*command, &payload)) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        if (command->id() == kCommandTabClosed ||
            command->id() == kCommandTabClosedObsolete) {
          delete GetTab(payload.id, tabs);
          tabs->erase(payload.id);
        } else {
          delete GetWindow(payload.id, windows);
          windows->erase(payload.id);
        }
        break;
      }

      case kCommandTabNavigationPathPrunedFromBack: {
        TabNavigationPathPrunedFromBackPayload payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        SessionTab* tab = GetTab(payload.id, tabs);
        tab->navigations.erase(
            FindClosestNavigationWithIndex(&(tab->navigations), payload.index),
            tab->navigations.end());
        break;
      }

      case kCommandTabNavigationPathPrunedFromFront: {
        TabNavigationPathPrunedFromFrontPayload payload;
        if (!command->GetPayload(&payload, sizeof(payload)) ||
            payload.index <= 0) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        SessionTab* tab = GetTab(payload.id, tabs);

        // Update the selected navigation index.
        tab->current_navigation_index =
            std::max(-1, tab->current_navigation_index - payload.index);

        // And update the index of existing navigations.
        for (std::vector<SerializedNavigationEntry>::iterator
                 i = tab->navigations.begin();
             i != tab->navigations.end();) {
          i->set_index(i->index() - payload.index);
          if (i->index() < 0)
            i = tab->navigations.erase(i);
          else
            ++i;
        }
        break;
      }

      case kCommandUpdateTabNavigation: {
        SerializedNavigationEntry navigation;
        SessionID::id_type tab_id;
        if (!RestoreUpdateTabNavigationCommand(
                *command, &navigation, &tab_id)) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        SessionTab* tab = GetTab(tab_id, tabs);
        std::vector<SerializedNavigationEntry>::iterator i =
            FindClosestNavigationWithIndex(&(tab->navigations),
                                           navigation.index());
        if (i != tab->navigations.end() && i->index() == navigation.index())
          *i = navigation;
        else
          tab->navigations.insert(i, navigation);
        break;
      }

      case kCommandSetSelectedNavigationIndex: {
        SelectedNavigationIndexPayload payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetTab(payload.id, tabs)->current_navigation_index = payload.index;
        break;
      }

      case kCommandSetSelectedTabInIndex: {
        SelectedTabInIndexPayload payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetWindow(payload.id, windows)->selected_tab_index = payload.index;
        break;
      }

      case kCommandSetWindowType: {
        WindowTypePayload payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetWindow(payload.id, windows)->is_constrained = false;
        GetWindow(payload.id, windows)->type =
            BrowserTypeForWindowType(
                static_cast<WindowType>(payload.index));
        break;
      }

      case kCommandSetPinnedState: {
        PinnedStatePayload payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        GetTab(payload.tab_id, tabs)->pinned = payload.pinned_state;
        break;
      }

      case kCommandSetWindowAppName: {
        SessionID::id_type window_id;
        std::string app_name;
        if (!RestoreSetWindowAppNameCommand(*command, &window_id, &app_name))
          return true;

        GetWindow(window_id, windows)->app_name.swap(app_name);
        break;
      }

      case kCommandSetExtensionAppID: {
        SessionID::id_type tab_id;
        std::string extension_app_id;
        if (!RestoreSetTabExtensionAppIDCommand(
                *command, &tab_id, &extension_app_id)) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }

        GetTab(tab_id, tabs)->extension_app_id.swap(extension_app_id);
        break;
      }

      case kCommandSetTabUserAgentOverride: {
        SessionID::id_type tab_id;
        std::string user_agent_override;
        if (!RestoreSetTabUserAgentOverrideCommand(
                *command, &tab_id, &user_agent_override)) {
          return true;
        }

        GetTab(tab_id, tabs)->user_agent_override.swap(user_agent_override);
        break;
      }

      case kCommandSessionStorageAssociated: {
        scoped_ptr<Pickle> command_pickle(command->PayloadAsPickle());
        SessionID::id_type command_tab_id;
        std::string session_storage_persistent_id;
        PickleIterator iter(*command_pickle.get());
        if (!command_pickle->ReadInt(&iter, &command_tab_id) ||
            !command_pickle->ReadString(&iter, &session_storage_persistent_id))
          return true;
        // Associate the session storage back.
        GetTab(command_tab_id, tabs)->session_storage_persistent_id =
            session_storage_persistent_id;
        break;
      }

      case kCommandSetActiveWindow: {
        ActiveWindowPayload payload;
        if (!command->GetPayload(&payload, sizeof(payload))) {
          VLOG(1) << "Failed reading command " << command->id();
          return true;
        }
        *active_window_id = payload;
        break;
      }

      default:
        VLOG(1) << "Failed reading an unknown command " << command->id();
        return true;
    }
  }
  return true;
}

void SessionService::BuildCommandsForTab(const SessionID& window_id,
                                         WebContents* tab,
                                         int index_in_window,
                                         bool is_pinned,
                                         std::vector<SessionCommand*>* commands,
                                         IdToRange* tab_to_available_range) {
  DCHECK(tab && commands && window_id.id());
  SessionTabHelper* session_tab_helper = SessionTabHelper::FromWebContents(tab);
  const SessionID& session_id(session_tab_helper->session_id());
  commands->push_back(CreateSetTabWindowCommand(window_id, session_id));

  const int current_index = tab->GetController().GetCurrentEntryIndex();
  const int min_index = std::max(0,
                                 current_index - max_persist_navigation_count);
  const int max_index =
      std::min(current_index + max_persist_navigation_count,
               tab->GetController().GetEntryCount());
  const int pending_index = tab->GetController().GetPendingEntryIndex();
  if (tab_to_available_range) {
    (*tab_to_available_range)[session_id.id()] =
        std::pair<int, int>(min_index, max_index);
  }

  if (is_pinned) {
    commands->push_back(CreatePinnedStateCommand(session_id, true));
  }

  extensions::TabHelper* extensions_tab_helper =
      extensions::TabHelper::FromWebContents(tab);
  if (extensions_tab_helper->extension_app()) {
    commands->push_back(
        CreateSetTabExtensionAppIDCommand(
            kCommandSetExtensionAppID, session_id.id(),
            extensions_tab_helper->extension_app()->id()));
  }

  const std::string& ua_override = tab->GetUserAgentOverride();
  if (!ua_override.empty()) {
    commands->push_back(
        CreateSetTabUserAgentOverrideCommand(
            kCommandSetTabUserAgentOverride, session_id.id(), ua_override));
  }

  for (int i = min_index; i < max_index; ++i) {
    const NavigationEntry* entry = (i == pending_index) ?
        tab->GetController().GetPendingEntry() :
        tab->GetController().GetEntryAtIndex(i);
    DCHECK(entry);
    if (ShouldTrackEntry(entry->GetVirtualURL())) {
      const SerializedNavigationEntry navigation =
          SerializedNavigationEntry::FromNavigationEntry(i, *entry);
      commands->push_back(
          CreateUpdateTabNavigationCommand(
              kCommandUpdateTabNavigation, session_id.id(), navigation));
    }
  }
  commands->push_back(
      CreateSetSelectedNavigationIndexCommand(session_id, current_index));

  if (index_in_window != -1) {
    commands->push_back(
        CreateSetTabIndexInWindowCommand(session_id, index_in_window));
  }

  // Record the association between the sessionStorage namespace and the tab.
  content::SessionStorageNamespace* session_storage_namespace =
      tab->GetController().GetDefaultSessionStorageNamespace();
  ScheduleCommand(CreateSessionStorageAssociatedCommand(
      session_tab_helper->session_id(),
      session_storage_namespace->persistent_id()));
}

void SessionService::BuildCommandsForBrowser(
    Browser* browser,
    std::vector<SessionCommand*>* commands,
    IdToRange* tab_to_available_range,
    std::set<SessionID::id_type>* windows_to_track) {
  DCHECK(browser && commands);
  DCHECK(browser->session_id().id());

  commands->push_back(
      CreateSetWindowBoundsCommand(browser->session_id(),
                                   browser->window()->GetRestoredBounds(),
                                   browser->window()->GetRestoredState()));

  commands->push_back(CreateSetWindowTypeCommand(
      browser->session_id(), WindowTypeForBrowserType(browser->type())));

  if (!browser->app_name().empty()) {
    commands->push_back(CreateSetWindowAppNameCommand(
        kCommandSetWindowAppName,
        browser->session_id().id(),
        browser->app_name()));
  }

  windows_to_track->insert(browser->session_id().id());
  TabStripModel* tab_strip = browser->tab_strip_model();
  for (int i = 0; i < tab_strip->count(); ++i) {
    WebContents* tab = tab_strip->GetWebContentsAt(i);
    DCHECK(tab);
    BuildCommandsForTab(browser->session_id(), tab, i,
                        tab_strip->IsTabPinned(i),
                        commands, tab_to_available_range);
  }

  commands->push_back(
      CreateSetSelectedTabInWindow(browser->session_id(),
                                   browser->tab_strip_model()->active_index()));
}

void SessionService::BuildCommandsFromBrowsers(
    std::vector<SessionCommand*>* commands,
    IdToRange* tab_to_available_range,
    std::set<SessionID::id_type>* windows_to_track) {
  DCHECK(commands);
  for (chrome::BrowserIterator it; !it.done(); it.Next()) {
    Browser* browser = *it;
    // Make sure the browser has tabs and a window. Browser's destructor
    // removes itself from the BrowserList. When a browser is closed the
    // destructor is not necessarily run immediately. This means it's possible
    // for us to get a handle to a browser that is about to be removed. If
    // the tab count is 0 or the window is NULL, the browser is about to be
    // deleted, so we ignore it.
    if (ShouldTrackBrowser(browser) && browser->tab_strip_model()->count() &&
        browser->window()) {
      BuildCommandsForBrowser(browser, commands, tab_to_available_range,
                              windows_to_track);
    }
  }
}

void SessionService::ScheduleReset() {
  set_pending_reset(true);
  STLDeleteElements(&pending_commands());
  tab_to_available_range_.clear();
  windows_tracking_.clear();
  BuildCommandsFromBrowsers(&pending_commands(), &tab_to_available_range_,
                            &windows_tracking_);
  if (!windows_tracking_.empty()) {
    // We're lazily created on startup and won't get an initial batch of
    // SetWindowType messages. Set these here to make sure our state is correct.
    has_open_trackable_browsers_ = true;
    move_on_new_browser_ = true;
  }
  StartSaveTimer();
}

bool SessionService::ReplacePendingCommand(SessionCommand* command) {
  // We optimize page navigations, which can happen quite frequently and
  // are expensive. And activation is like Highlander, there can only be one!
  if (command->id() != kCommandUpdateTabNavigation &&
      command->id() != kCommandSetActiveWindow) {
    return false;
  }
  for (std::vector<SessionCommand*>::reverse_iterator i =
       pending_commands().rbegin(); i != pending_commands().rend(); ++i) {
    SessionCommand* existing_command = *i;
    if (command->id() == kCommandUpdateTabNavigation &&
        existing_command->id() == kCommandUpdateTabNavigation) {
      scoped_ptr<Pickle> command_pickle(command->PayloadAsPickle());
      PickleIterator iterator(*command_pickle);
      SessionID::id_type command_tab_id;
      int command_nav_index;
      if (!command_pickle->ReadInt(&iterator, &command_tab_id) ||
          !command_pickle->ReadInt(&iterator, &command_nav_index)) {
        return false;
      }
      SessionID::id_type existing_tab_id;
      int existing_nav_index;
      {
        // Creating a pickle like this means the Pickle references the data from
        // the command. Make sure we delete the pickle before the command, else
        // the pickle references deleted memory.
        scoped_ptr<Pickle> existing_pickle(existing_command->PayloadAsPickle());
        iterator = PickleIterator(*existing_pickle);
        if (!existing_pickle->ReadInt(&iterator, &existing_tab_id) ||
            !existing_pickle->ReadInt(&iterator, &existing_nav_index)) {
          return false;
        }
      }
      if (existing_tab_id == command_tab_id &&
          existing_nav_index == command_nav_index) {
        // existing_command is an update for the same tab/index pair. Replace
        // it with the new one. We need to add to the end of the list just in
        // case there is a prune command after the update command.
        delete existing_command;
        pending_commands().erase(i.base() - 1);
        pending_commands().push_back(command);
        return true;
      }
      return false;
    }
    if (command->id() == kCommandSetActiveWindow &&
        existing_command->id() == kCommandSetActiveWindow) {
      *i = command;
      delete existing_command;
      return true;
    }
  }
  return false;
}

void SessionService::ScheduleCommand(SessionCommand* command) {
  DCHECK(command);
  if (ReplacePendingCommand(command))
    return;
  BaseSessionService::ScheduleCommand(command);
  // Don't schedule a reset on tab closed/window closed. Otherwise we may
  // lose tabs/windows we want to restore from if we exit right after this.
  if (!pending_reset() && pending_window_close_ids_.empty() &&
      commands_since_reset() >= kWritesPerReset &&
      (command->id() != kCommandTabClosed &&
       command->id() != kCommandWindowClosed)) {
    ScheduleReset();
  }
}

void SessionService::CommitPendingCloses() {
  for (PendingTabCloseIDs::iterator i = pending_tab_close_ids_.begin();
       i != pending_tab_close_ids_.end(); ++i) {
    ScheduleCommand(CreateTabClosedCommand(*i));
  }
  pending_tab_close_ids_.clear();

  for (PendingWindowCloseIDs::iterator i = pending_window_close_ids_.begin();
       i != pending_window_close_ids_.end(); ++i) {
    ScheduleCommand(CreateWindowClosedCommand(*i));
  }
  pending_window_close_ids_.clear();
}

bool SessionService::IsOnlyOneTabLeft() const {
  if (!profile() || profile()->AsTestingProfile()) {
    // We're testing, always return false.
    return false;
  }

  int window_count = 0;
  for (chrome::BrowserIterator it; !it.done(); it.Next()) {
    Browser* browser = *it;
    const SessionID::id_type window_id = browser->session_id().id();
    if (ShouldTrackBrowser(browser) &&
        window_closing_ids_.find(window_id) == window_closing_ids_.end()) {
      if (++window_count > 1)
        return false;
      // By the time this is invoked the tab has been removed. As such, we use
      // > 0 here rather than > 1.
      if (browser->tab_strip_model()->count() > 0)
        return false;
    }
  }
  return true;
}

bool SessionService::HasOpenTrackableBrowsers(
    const SessionID& window_id) const {
  if (!profile() || profile()->AsTestingProfile()) {
    // We're testing, always return true.
    return true;
  }

  for (chrome::BrowserIterator it; !it.done(); it.Next()) {
    Browser* browser = *it;
    const SessionID::id_type browser_id = browser->session_id().id();
    if (browser_id != window_id.id() &&
        window_closing_ids_.find(browser_id) == window_closing_ids_.end() &&
        ShouldTrackBrowser(browser)) {
      return true;
    }
  }
  return false;
}

bool SessionService::ShouldTrackChangesToWindow(
    const SessionID& window_id) const {
  return windows_tracking_.find(window_id.id()) != windows_tracking_.end();
}

bool SessionService::ShouldTrackBrowser(Browser* browser) const {
  AppType app_type = browser->is_app() ? TYPE_APP : TYPE_NORMAL;
  return browser->profile() == profile() &&
         should_track_changes_for_browser_type(browser->type(), app_type);
}

bool SessionService::should_track_changes_for_browser_type(Browser::Type type,
                                                           AppType app_type) {
#if defined(OS_CHROMEOS)
  // Restore app popups for chromeos alone.
  if (type == Browser::TYPE_POPUP && app_type == TYPE_APP)
    return true;
#endif

  return type == Browser::TYPE_TABBED ||
        (type == Browser::TYPE_POPUP && browser_defaults::kRestorePopups);
}

SessionService::WindowType SessionService::WindowTypeForBrowserType(
    Browser::Type type) {
  switch (type) {
    case Browser::TYPE_POPUP:
      return TYPE_POPUP;
    case Browser::TYPE_TABBED:
      return TYPE_TABBED;
    default:
      DCHECK(false);
      return TYPE_TABBED;
  }
}

Browser::Type SessionService::BrowserTypeForWindowType(WindowType type) {
  switch (type) {
    case TYPE_POPUP:
      return Browser::TYPE_POPUP;
    case TYPE_TABBED:
    default:
      return Browser::TYPE_TABBED;
  }
}

void SessionService::RecordSessionUpdateHistogramData(int type,
    base::TimeTicks* last_updated_time) {
  if (!last_updated_time->is_null()) {
    base::TimeDelta delta = base::TimeTicks::Now() - *last_updated_time;
    // We're interested in frequent updates periods longer than
    // 10 minutes.
    bool use_long_period = false;
    if (delta >= save_delay_in_mins_) {
      use_long_period = true;
    }
    switch (type) {
      case chrome::NOTIFICATION_SESSION_SERVICE_SAVED :
        RecordUpdatedSaveTime(delta, use_long_period);
        RecordUpdatedSessionNavigationOrTab(delta, use_long_period);
        break;
      case content::NOTIFICATION_WEB_CONTENTS_DESTROYED:
        RecordUpdatedTabClosed(delta, use_long_period);
        RecordUpdatedSessionNavigationOrTab(delta, use_long_period);
        break;
      case content::NOTIFICATION_NAV_LIST_PRUNED:
        RecordUpdatedNavListPruned(delta, use_long_period);
        RecordUpdatedSessionNavigationOrTab(delta, use_long_period);
        break;
      case content::NOTIFICATION_NAV_ENTRY_COMMITTED:
        RecordUpdatedNavEntryCommit(delta, use_long_period);
        RecordUpdatedSessionNavigationOrTab(delta, use_long_period);
        break;
      default:
        NOTREACHED() << "Bad type sent to RecordSessionUpdateHistogramData";
        break;
    }
  }
  (*last_updated_time) = base::TimeTicks::Now();
}

void SessionService::RecordUpdatedTabClosed(base::TimeDelta delta,
                                            bool use_long_period) {
  std::string name("SessionRestore.TabClosedPeriod");
  UMA_HISTOGRAM_CUSTOM_TIMES(name,
      delta,
      // 2500ms is the default save delay.
      save_delay_in_millis_,
      save_delay_in_mins_,
      50);
  if (use_long_period) {
    std::string long_name_("SessionRestore.TabClosedLongPeriod");
    UMA_HISTOGRAM_CUSTOM_TIMES(long_name_,
        delta,
        save_delay_in_mins_,
        save_delay_in_hrs_,
        50);
  }
}

void SessionService::RecordUpdatedNavListPruned(base::TimeDelta delta,
                                                bool use_long_period) {
  std::string name("SessionRestore.NavigationListPrunedPeriod");
  UMA_HISTOGRAM_CUSTOM_TIMES(name,
      delta,
      // 2500ms is the default save delay.
      save_delay_in_millis_,
      save_delay_in_mins_,
      50);
  if (use_long_period) {
    std::string long_name_("SessionRestore.NavigationListPrunedLongPeriod");
    UMA_HISTOGRAM_CUSTOM_TIMES(long_name_,
        delta,
        save_delay_in_mins_,
        save_delay_in_hrs_,
        50);
  }
}

void SessionService::RecordUpdatedNavEntryCommit(base::TimeDelta delta,
                                                 bool use_long_period) {
  std::string name("SessionRestore.NavEntryCommittedPeriod");
  UMA_HISTOGRAM_CUSTOM_TIMES(name,
      delta,
      // 2500ms is the default save delay.
      save_delay_in_millis_,
      save_delay_in_mins_,
      50);
  if (use_long_period) {
    std::string long_name_("SessionRestore.NavEntryCommittedLongPeriod");
    UMA_HISTOGRAM_CUSTOM_TIMES(long_name_,
        delta,
        save_delay_in_mins_,
        save_delay_in_hrs_,
        50);
  }
}

void SessionService::RecordUpdatedSessionNavigationOrTab(base::TimeDelta delta,
                                                         bool use_long_period) {
  std::string name("SessionRestore.NavOrTabUpdatePeriod");
  UMA_HISTOGRAM_CUSTOM_TIMES(name,
      delta,
      // 2500ms is the default save delay.
      save_delay_in_millis_,
      save_delay_in_mins_,
      50);
  if (use_long_period) {
    std::string long_name_("SessionRestore.NavOrTabUpdateLongPeriod");
    UMA_HISTOGRAM_CUSTOM_TIMES(long_name_,
        delta,
        save_delay_in_mins_,
        save_delay_in_hrs_,
        50);
  }
}

void SessionService::RecordUpdatedSaveTime(base::TimeDelta delta,
                                           bool use_long_period) {
  std::string name("SessionRestore.SavePeriod");
  UMA_HISTOGRAM_CUSTOM_TIMES(name,
      delta,
      // 2500ms is the default save delay.
      save_delay_in_millis_,
      save_delay_in_mins_,
      50);
  if (use_long_period) {
    std::string long_name_("SessionRestore.SaveLongPeriod");
    UMA_HISTOGRAM_CUSTOM_TIMES(long_name_,
        delta,
        save_delay_in_mins_,
        save_delay_in_hrs_,
        50);
  }
}

void SessionService::TabInserted(WebContents* contents) {
  SessionTabHelper* session_tab_helper =
      SessionTabHelper::FromWebContents(contents);
  if (!ShouldTrackChangesToWindow(session_tab_helper->window_id()))
    return;
  SetTabWindow(session_tab_helper->window_id(),
               session_tab_helper->session_id());
  extensions::TabHelper* extensions_tab_helper =
      extensions::TabHelper::FromWebContents(contents);
  if (extensions_tab_helper &&
      extensions_tab_helper->extension_app()) {
    SetTabExtensionAppID(
        session_tab_helper->window_id(),
        session_tab_helper->session_id(),
        extensions_tab_helper->extension_app()->id());
  }

  // Record the association between the SessionStorageNamespace and the
  // tab.
  //
  // TODO(ajwong): This should be processing the whole map rather than
  // just the default. This in particular will not work for tabs with only
  // isolated apps which won't have a default partition.
  content::SessionStorageNamespace* session_storage_namespace =
      contents->GetController().GetDefaultSessionStorageNamespace();
  ScheduleCommand(CreateSessionStorageAssociatedCommand(
      session_tab_helper->session_id(),
      session_storage_namespace->persistent_id()));
  session_storage_namespace->SetShouldPersist(true);
}

void SessionService::TabClosing(WebContents* contents) {
  // Allow the associated sessionStorage to get deleted; it won't be needed
  // in the session restore.
  content::SessionStorageNamespace* session_storage_namespace =
      contents->GetController().GetDefaultSessionStorageNamespace();
  session_storage_namespace->SetShouldPersist(false);
  SessionTabHelper* session_tab_helper =
      SessionTabHelper::FromWebContents(contents);
  TabClosed(session_tab_helper->window_id(),
            session_tab_helper->session_id(),
            contents->GetClosedByUserGesture());
  RecordSessionUpdateHistogramData(content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
                                   &last_updated_tab_closed_time_);
}

void SessionService::MaybeDeleteSessionOnlyData() {
  // Don't try anything if we're testing.  The browser_process is not fully
  // created and DeleteSession will crash if we actually attempt it.
  if (!profile() || profile()->AsTestingProfile())
    return;

  // Clear session data if the last window for a profile has been closed and
  // closing the last window would normally close Chrome, unless background mode
  // is active.  Tests don't have a background_mode_manager.
  if (has_open_trackable_browsers_ ||
      browser_defaults::kBrowserAliveWithNoWindows ||
      g_browser_process->background_mode_manager()->IsBackgroundModeActive()) {
    return;
  }

  // Check for any open windows for the current profile that we aren't tracking.
  for (chrome::BrowserIterator it; !it.done(); it.Next()) {
    if ((*it)->profile() == profile())
      return;
  }
  DeleteSessionOnlyData(profile());
}
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root/chrome/browser/sessions/session_service.cc

DEFINITIONS
