root/chrome/browser/extensions/api/extension_action/

1. browser_action_apitest.cc
2. browser_action_browsertest.cc
3. browser_action_interactive_test.cc
4. extension_action_api.cc
5. extension_action_api.h
6. extension_action_prefs_unittest.cc
7. extension_page_actions_api_constants.cc
8. extension_page_actions_api_constants.h
9. page_action_apitest.cc