Acknowledge invalidations from DriveFileSyncService.

In r186079, local invalidations and acknowledgements were fully
implemented. This means that if an InvalidationHandler doesn't
acknowledge invalidations that it receives, it will receive wake up
pings periodically afterwards.

BUG=180693


Review URL: https://chromiumcodereview.appspot.com/13913018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193410 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/sync_file_system/drive_file_sync_service.cc

@@ -167,6 +167,14 @@ void DriveFileSyncService::OnIncomingInvalidation(
       ipc::invalidation::ObjectSource::COSMO_CHANGELOG,
       kDriveInvalidationObjectId);
   DCHECK_EQ(1U, invalidation_map.count(object_id));
+  // TODO(dcheng): Only acknowledge the invalidation once the fetch has
+  // completed. http://crbug.com/156843
+  ProfileSyncService* profile_sync_service =
+      ProfileSyncServiceFactory::GetForProfile(profile_);
+  CHECK(profile_sync_service);
+  profile_sync_service->AcknowledgeInvalidation(
+      invalidation_map.begin()->first,
+      invalidation_map.begin()->second.ack_handle);
 
   may_have_unfetched_changes_ = true;
   MaybeStartFetchChanges();