Hold the Pepper proxy lock for all Pepper GL calls.

ppapi/proxy/ppapi_command_buffer_proxy.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 "ppapi/proxy/ppapi_command_buffer_proxy.h"
 
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/proxy_channel.h"
 #include "ppapi/shared_impl/api_id.h"
 #include "ppapi/shared_impl/host_resource.h"
@@ skipping 201 matching lines @@
     size_t height,
     unsigned internalformat,
     unsigned usage) {
   NOTREACHED();
   return -1;
 }
 
 bool PpapiCommandBufferProxy::Send(IPC::Message* msg) {
   DCHECK(last_state_.error == gpu::error::kNoError);
 
-  if (channel_->Send(msg))
+  // We need hold the Pepper proxy lock for sync IPC, because GPU command buffer
+  // may use a sync IPC with another lock held. It may cause deadlock.
+  // http://crbug.com/418651
+  if (channel_->SendAndStayLocked(msg))
     return true;
 
   last_state_.error = gpu::error::kLostContext;
   return false;
 }
 
 void PpapiCommandBufferProxy::UpdateState(
     const gpu::CommandBuffer::State& state,
     bool success) {
   // Handle wraparound. It works as long as we don't have more than 2B state
@@ skipping 13 matching lines @@
     shared_state()->Read(&last_state_);
 }
 
 gpu::CommandBufferSharedState* PpapiCommandBufferProxy::shared_state() const {
   return reinterpret_cast<gpu::CommandBufferSharedState*>(
       shared_state_shm_->memory());
 }
 
 }  // namespace proxy
 }  // namespace ppapi