Add SNAPSHOT sync mode to LocalFileSyncContext::PrepareForSync

chrome/browser/sync_file_system/local/local_file_change_tracker.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_LOCAL_LOCAL_FILE_CHANGE_TRACKER_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_LOCAL_LOCAL_FILE_CHANGE_TRACKER_H_
 
 #include <deque>
 #include <map>
 #include <string>
@@ skipping 57 matching lines @@
                           int max_urls);
 
   // Returns all changes recorded for the given |url|.
   // This should be called after writing is disabled.
   void GetChangesForURL(const fileapi::FileSystemURL& url,
                         FileChangeList* changes);
 
   // Clears the pending changes recorded in this tracker for |url|.
   void ClearChangesForURL(const fileapi::FileSystemURL& url);
 
+  // Creates a fresh (empty) in-memory record for |url|.
+  // Note that new changes are recorded to the mirror too.
+  void CreateFreshMirrorForURL(const fileapi::FileSystemURL& url);
+
+  // Removes a mirror for |url|, and commits the change status to database.
+  void RemoveMirrorAndCommitChangesForURL(const fileapi::FileSystemURL& url);
+
+  // Resets the changes to the ones recorded in mirror for |url|, and
+  // commits the updated change status to database.
+  void ResetToMirrorAndCommitChangesForURL(const fileapi::FileSystemURL& url);
+
   // Called by FileSyncService at the startup time to restore last dirty changes
   // left after the last shutdown (if any).
   SyncStatusCode Initialize(fileapi::FileSystemContext* file_system_context);
 
   // This method is (exceptionally) thread-safe.
   int64 num_changes() const {
     base::AutoLock lock(num_changes_lock_);
     return num_changes_;
   }
 
@@ skipping 28 matching lines @@
 
   // Database related methods.
   SyncStatusCode MarkDirtyOnDatabase(const fileapi::FileSystemURL& url);
   SyncStatusCode ClearDirtyOnDatabase(const fileapi::FileSystemURL& url);
 
   SyncStatusCode CollectLastDirtyChanges(
       fileapi::FileSystemContext* file_system_context);
   void RecordChange(const fileapi::FileSystemURL& url,
                     const FileChange& change);
 
+  static void RecordChangeToChangeMaps(const fileapi::FileSystemURL& url,
+                                       const FileChange& change,
+                                       int change_seq,
+                                       FileChangeMap* changes,
+                                       ChangeSeqMap* change_seqs);
+
   bool initialized_;
 
   scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
 
   FileChangeMap changes_;
   ChangeSeqMap change_seqs_;
 
+  // For mirrors.
+  FileChangeMap mirror_changes_;
+
   scoped_ptr<TrackerDB> tracker_db_;
 
   // Change sequence number. Briefly gives a hint about the order of changes,
   // but they are updated when a new change comes on the same file (as
   // well as Drive's changestamps).
   int64 current_change_seq_;
 
   // This can be accessed on any threads (with num_changes_lock_).
   int64 num_changes_;
   mutable base::Lock num_changes_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(LocalFileChangeTracker);
 };
 
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_LOCAL_LOCAL_FILE_CHANGE_TRACKER_H_