Fix the mac hangup when force-compositing-mode is enabled

content/common/gpu/gpu_command_buffer_stub.h

 // Copyright (c) 2011 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 CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 #define CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 #pragma once
 
 #if defined(ENABLE_GPU)
 
@@ skipping 59 matching lines @@
   void OnCompositorWindowPainted();
 #endif  // defined(OS_WIN)
 
   void ViewResized();
 
 #if defined(OS_MACOSX)
   // Called only by the GpuChannel.
   void AcceleratedSurfaceBuffersSwapped(uint64 swap_buffers_count);
 #endif  // defined(OS_MACOSX)
 
+  // Called when the command buffer was destroyed, and the stub should now
+  // unblock itself and handle pending messages.
+  void CommandBufferWasDestroyed();
+
  private:
   // Message handlers:
   void OnInitialize(base::SharedMemoryHandle ring_buffer,
                     int32 size,
                     IPC::Message* reply_message);
   void OnGetState(IPC::Message* reply_message);
   void OnFlush(int32 put_offset,
                int32 last_known_get,
                uint32 flush_count,
                IPC::Message* reply_message);
@@ skipping 48 matching lines @@
 
   GpuWatchdog* watchdog_;
   ScopedRunnableMethodFactory<GpuCommandBufferStub> task_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuCommandBufferStub);
 };
 
 #endif  // defined(ENABLE_GPU)
 
 #endif  // CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_