gpu: Move GpuWatchdogThread into //gpu/ipc/service from content.

gpu/ipc/service/gpu_watchdog.h

-// Copyright (c) 2012 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 GPU_IPC_SERVICE_GPU_WATCHDOG_H_
-#define GPU_IPC_SERVICE_GPU_WATCHDOG_H_
-
-#include "base/macros.h"
-
-namespace gpu {
-
-// Interface for objects that monitor the a GPUProcessor's progress. The
-// GPUProcessor will regularly invoke CheckArmed.
-class GpuWatchdog {
- public:
-  virtual void CheckArmed() = 0;
-
- protected:
-  GpuWatchdog() {}
-  virtual ~GpuWatchdog() {};
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(GpuWatchdog);
-};
-
-}  // namespace gpu
-
-#endif  // GPU_IPC_SERVICE_GPU_WATCHDOG_H_