[SyncFS] Demote local file changes before local-to-remote sync (3/3)

chrome/browser/sync_file_system/drive_backend/drive_backend_sync_unittest.cc

 // Copyright 2014 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 <algorithm>
 #include <stack>
 
 #include "base/file_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 322 matching lines @@
   void FetchRemoteChanges() {
     remote_sync_service_->OnNotificationReceived();
     WaitForIdleWorker();
   }
 
   SyncStatusCode ProcessChangesUntilDone() {
     int task_limit = 100;
     SyncStatusCode local_sync_status;
     SyncStatusCode remote_sync_status;
     while (true) {
+      base::RunLoop().RunUntilIdle();
+      WaitForIdleWorker();
+
       if (!task_limit--)
         return SYNC_STATUS_ABORT;
 
       local_sync_status = ProcessLocalChange();
       if (local_sync_status != SYNC_STATUS_OK &&
           local_sync_status != SYNC_STATUS_NO_CHANGE_TO_SYNC &&
           local_sync_status != SYNC_STATUS_FILE_BUSY)
         return local_sync_status;
 
       remote_sync_status = ProcessRemoteChange();
@@ skipping 1368 matching lines @@
 
   EXPECT_EQ(1u, CountApp());
   EXPECT_EQ(1u, CountLocalFile(app_id));
 
   EXPECT_EQ(2u, CountMetadata());
   EXPECT_EQ(2u, CountTracker());
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system