[Reland 1] Pepper takes ownership of a mailbox before passing it to the texture layer.

gpu/ipc/service/gpu_channel.cc

 // 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.
 
 #include "gpu/ipc/service/gpu_channel.h"
 
 #include <utility>
 
 #if defined(OS_WIN)
 #include <windows.h>
@@ skipping 222 matching lines @@
   if (scheduled_)
     channel_->PostHandleMessage(this);
 
   sync_point_order_data_->PauseProcessingOrderNumber(
       channel_messages_.front()->order_number);
 }
 
 void GpuChannelMessageQueue::FinishMessageProcessing() {
   base::AutoLock auto_lock(channel_lock_);
   DCHECK(!channel_messages_.empty());
-  DCHECK(scheduled_);

[erikchen, 2016/05/03 17:24:14]

This assertion is no longer valid, since OnWaitSyncToken can leave the channel
descheduled.

 
   sync_point_order_data_->FinishProcessingOrderNumber(
       channel_messages_.front()->order_number);
   channel_messages_.pop_front();
 
   if (!channel_messages_.empty())
     channel_->PostHandleMessage(this);
 
   if (preempting_flag_) {
     io_task_runner_->PostTask(
@@ skipping 795 matching lines @@
           ->CreateImageForGpuMemoryBuffer(handle,
                                           size,
                                           format,
                                           internalformat,
                                           client_id_);
     }
   }
 }
 
 }  // namespace gpu