[SyncFileSystem] Add MetadataDatabase::TryNoSideEffectActivation

chrome/browser/sync_file_system/drive_backend/metadata_database.h

 // Copyright 2013 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.
 
 #ifndef CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_METADATA_DATABASE_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_METADATA_DATABASE_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 255 matching lines @@
   // If the tracker has no further change to sync, unmarks its dirty flag.
   void PopulateFolderByChildList(const std::string& folder_id,
                                  const FileIDList& child_file_ids,
                                  const SyncStatusCallback& callback);
 
   // Updates |synced_details| of the tracker with |updated_details|.
   void UpdateTracker(int64 tracker_id,
                      const FileDetails& updated_details,
                      const SyncStatusCallback& callback);
 
+  // Returns true if the tracker can be safely activated without deactivating
+  // any other trackers.  In this case, tries to activate the tracker, and
+  // invokes |callback| upon completion.
+  // Returns false otherwise.  In false case, |callback| will not be invoked.
+  bool TryNoSideEffectActivation(int64 tracker_id,
+                                 const SyncStatusCallback& callback);
+
   // Changes the priority of the tracker to low.
   void LowerTrackerPriority(int64 tracker_id);
   void PromoteLowerPriorityTrackersToNormal();
 
   // Returns true if there is a normal priority dirty tracker.
   // Assigns the dirty tracker if exists and |tracker| is non-NULL.
   bool GetNormalPriorityDirtyTracker(FileTracker* tracker) const;
 
   // Returns true if there is a low priority dirty tracker.
   // Assigns the dirty tracker if exists and |tracker| is non-NULL.
@@ skipping 137 matching lines @@
 
   base::WeakPtrFactory<MetadataDatabase> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MetadataDatabase);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_METADATA_DATABASE_H_