PPAPI: Make GLES2 calls resilient to bad/dead resources.

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 56 matching lines @@
     if (Send(new PpapiHostMsg_PPBGraphics3D_GetState(
              ppapi::API_ID_PPB_GRAPHICS_3D, resource_, &state, &success))) {
       UpdateState(state, success);
     }
   }
 
   return last_state_;
 }
 
 gpu::CommandBuffer::State PpapiCommandBufferProxy::GetLastState() {
-  // Note: The locking command buffer wrapper does not take a global lock before
-  // calling this function.
   return last_state_;
 }
 
 int32 PpapiCommandBufferProxy::GetLastToken() {
-  // Note: The locking command buffer wrapper does not take a global lock before
-  // calling this function.
   return last_state_.token;
 }
 
 void PpapiCommandBufferProxy::Flush(int32 put_offset) {
   if (last_state_.error != gpu::error::kNoError)
     return;
 
   IPC::Message* message = new PpapiHostMsg_PPBGraphics3D_AsyncFlush(
       ppapi::API_ID_PPB_GRAPHICS_3D, resource_, put_offset);
 
@@ skipping 155 matching lines @@
       last_state_ = state;
     }
   } else {
     last_state_.error = gpu::error::kLostContext;
     ++last_state_.generation;
   }
 }
 
 }  // namespace proxy
 }  // namespace ppapi