Introduce ThreadTaskRunnerHandle::OverrideForTesting and TestMockTimeTaskRunner::ScopedContext.

components/sync/driver/sync_stopped_reporter.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_SYNC_DRIVER_SYNC_STOPPED_REPORTER_H_
 #define COMPONENTS_SYNC_DRIVER_SYNC_STOPPED_REPORTER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 25 matching lines @@
 
   // Inform the sync server that sync was stopped on this device.
   // |access_token|, |cache_guid|, and |birthday| must not be empty.
   void ReportSyncStopped(const std::string& access_token,
                          const std::string& cache_guid,
                          const std::string& birthday);
 
   // net::URLFetcherDelegate implementation.
   void OnURLFetchComplete(const net::URLFetcher* source) override;
 
-  // Override the timer's task runner so it can be triggered in tests.
-  void SetTimerTaskRunnerForTest(
-      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
-
  private:
   // Convert the base sync URL into the sync event URL.
   static GURL GetSyncEventURL(const GURL& sync_service_url);
 
   // Callback for a request timing out.
   void OnTimeout();
 
   // Handles timing out requests.
   base::OneShotTimer timer_;
 
@@ skipping 11 matching lines @@
 
   // A callback for request completion or timeout.
   ResultCallback callback_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncStoppedReporter);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_SYNC_STOPPED_REPORTER_H_