AttachmentId       60 sync/api/attachments/attachment.h typedef std::map<AttachmentId, Attachment> AttachmentMap;
AttachmentId       40 sync/api/attachments/attachment_id.cc AttachmentId::~AttachmentId() {}
AttachmentId       74 sync/api/attachments/attachment_id.cc AttachmentId::AttachmentId(sync_pb::AttachmentIdProto* proto)