[Sync] Introduce SyncedSessionWindow type.

components/sync_sessions/sessions_sync_manager.h

Index: components/sync_sessions/sessions_sync_manager.h
diff --git a/components/sync_sessions/sessions_sync_manager.h b/components/sync_sessions/sessions_sync_manager.h
index 2513fc7a064c1dec4bc3a6d4e2f44bb92b14b091..bf72e9e716e296e8eb9c31f62402f28ea756e766 100644
--- a/components/sync_sessions/sessions_sync_manager.h
+++ b/components/sync_sessions/sessions_sync_manager.h
@@ -146,7 +146,6 @@ class SessionsSyncManager : public syncer::SyncableService,
   FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, SwappedOutOnRestore);
   FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest,
                            ProcessRemoteDeleteOfLocalSession);
-  FRIEND_TEST_ALL_PREFIXES(SessionsSyncManagerTest, SetVariationIds);
 
   void InitializeCurrentMachineTag(const std::string& cache_guid);
 
@@ -195,10 +194,11 @@ class SessionsSyncManager : public syncer::SyncableService,
 
   // Builds |session_window| from the session specifics window
   // provided and updates the SessionTracker with foreign session data created.
-  void BuildSyncedSessionFromSpecifics(const std::string& session_tag,
-                                       const sync_pb::SessionWindow& specifics,
-                                       base::Time mtime,
-                                       sessions::SessionWindow* session_window);
+  void BuildSyncedSessionFromSpecifics(
+      const std::string& session_tag,
+      const sync_pb::SessionWindow& specifics,
+      base::Time mtime,
+      SyncedSessionWindow* synced_session_window);
 
   // Resync local window information. Updates the local sessions header node
   // with the status of open windows and the order of tabs they contain. Should
@@ -230,10 +230,6 @@ class SessionsSyncManager : public syncer::SyncableService,
                                  base::Time mtime,
                                  sessions::SessionTab* session_tab);
 
-  // Sets |variation_ids| field of |session_tab| with the ids of the currently
-  // assigned variations which should be sent to sync.
-  static void SetVariationIds(sessions::SessionTab* session_tab);
-
   // Populates |specifics| based on the data in |tab_delegate|.
   void LocalTabDelegateToSpecifics(const SyncedTabDelegate& tab_delegate,
                                    sync_pb::SessionSpecifics* specifics);