[SyncFileSystem] Add MetadataDatabase::TryNoSideEffectActivation

chrome/browser/sync_file_system/drive_backend/metadata_database.cc

 // 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.
 
 #include "chrome/browser/sync_file_system/drive_backend/metadata_database.h"
 
 #include <algorithm>
 #include <stack>
 
 #include "base/bind.h"
@@ skipping 1023 matching lines @@
   if (tracker->dirty() && !ShouldKeepDirty(*tracker)) {
     tracker->set_dirty(false);
     dirty_trackers_.erase(tracker);
     low_priority_dirty_trackers_.erase(tracker);
   }
   PutTrackerToBatch(*tracker, batch.get());
 
   WriteToDatabase(batch.Pass(), callback);
 }
 
+bool MetadataDatabase::TryNoSideEffectActivation(
+    int64 tracker_id,
+    const SyncStatusCallback& callback) {
+  DCHECK(ContainsKey(tracker_by_id_, tracker_id));
+  const FileTracker& tracker = *tracker_by_id_[tracker_id];
+  if (tracker.active()) {
+    RunSoon(FROM_HERE, base::Bind(callback, SYNC_STATUS_OK));
+    return true;
+  }
+
+  if (!CanActivateTracker(tracker))
+    return false;
+
+  scoped_ptr<leveldb::WriteBatch> batch(new leveldb::WriteBatch);
+  MakeTrackerActive(tracker_id, batch.get());
+  WriteToDatabase(batch.Pass(), callback);
+  return true;
+}
+
 void MetadataDatabase::LowerTrackerPriority(int64 tracker_id) {
   TrackerByID::const_iterator found = tracker_by_id_.find(tracker_id);
   if (found == tracker_by_id_.end())
     return;
 
   FileTracker* tracker = found->second;
   if (dirty_trackers_.erase(tracker))
     low_priority_dirty_trackers_.insert(tracker);
 }
 
@@ skipping 705 matching lines @@
                                             int64 change_id) {
   FileByID::const_iterator found = file_by_id_.find(file_id);
   if (found == file_by_id_.end())
     return false;
   DCHECK(found->second->has_details());
   return found->second->details().change_id() >= change_id;
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system