Implement new invalidations ack tracking system

chrome/browser/sync/glue/sync_backend_host_core.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/glue/sync_backend_host_core.h"
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/metrics/histogram.h"
 #include "chrome/browser/sync/glue/device_info.h"
@@ skipping 306 matching lines @@
       sync_error);
 }
 
 void SyncBackendHostCore::DoOnInvalidatorStateChange(
     syncer::InvalidatorState state) {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   sync_manager_->OnInvalidatorStateChange(state);
 }
 
 void SyncBackendHostCore::DoOnIncomingInvalidation(
-    syncer::ObjectIdInvalidationMap invalidation_map) {
+    const syncer::ObjectIdInvalidationMap& invalidation_map) {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   sync_manager_->OnIncomingInvalidation(invalidation_map);
 }
 
 void SyncBackendHostCore::DoInitialize(
     scoped_ptr<DoInitializeOptions> options) {
   DCHECK(!sync_loop_);
   sync_loop_ = options->sync_loop;
   DCHECK(sync_loop_);
 
@@ skipping 275 matching lines @@
       this, &SyncBackendHostCore::SaveChanges);
 }
 
 void SyncBackendHostCore::SaveChanges() {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   sync_manager_->SaveChanges();
 }
 
 }  // namespace browser_sync