[SyncFS] Add MetadataDatabase::UpdateTracker

chrome/browser/sync_file_system/drive_backend/metadata_database.proto

 // 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.
 //
 // Protocol buffer definitions for Drive backend of Syncable FileSystem.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package sync_file_system.drive_backend;
 
 enum FileKind {
   FILE_KIND_UNSUPPORTED = 0;
   FILE_KIND_FILE = 1;
   FILE_KIND_FOLDER = 2;
 }
 
 enum TrackerKind {
   TRACKER_KIND_REGULAR = 0;
+
+  // TODO(tzik): Add TRACKER_KIND_DISABLED_REGULAR and keep all descendants of
+  // disabled app-root disabled.  Disabled trackers should be excluded from
+  // dirty_trackers_ and the sync-engine should not update them.
   TRACKER_KIND_APP_ROOT = 1;
   TRACKER_KIND_DISABLED_APP_ROOT = 2;
 }
 
 message ServiceMetadata {
   optional int64 largest_change_id = 1;
   optional int64 sync_root_tracker_id = 2;
 
   // The sequence number of FileTrackers. Must be positive.
   optional int64 next_tracker_id = 3;
@@ skipping 44 matching lines @@
   optional bool dirty = 7;
 
   // True if the FileTracker is active.
   // Remote file modification should only be applied to active trackers.
   // Active FileTracker must have a unique title under its parent.
   optional bool active = 8;
 
   // Valid only for folders.
   // True if the folder contents have not yet been fetched.
   optional bool needs_folder_listing = 9;
+
+  // True when the tracker has both remote change and local change.
+  // SyncEngine should process this change after all local change was processed.
+  optional bool priority_low = 10;

[kinuko, 2013/08/27 13:20:19]

Not used in this CL yet?

This name usually does not imply what the comment says.  If this flag is used
solely for the commented purpose should we rename the flag?  Or if it could be
used just to indicate it should be processed at later stages should the comment
be updated..?

[tzik, 2013/08/30 05:51:57]

Reverted.
It's just a merge failure in my local repo.

 }