gpu: Fix webview parent compositor crash in context loss

gpu/command_buffer/service/in_process_command_buffer.cc

 // Copyright 2013 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/command_buffer/service/in_process_command_buffer.h"
 
 #include <queue>
 #include <set>
 #include <utility>
 
@@ skipping 729 matching lines @@
 
 bool InProcessCommandBuffer::Initialize() {
   NOTREACHED();
   return false;
 }
 
 namespace {
 
 void PostCallback(const scoped_refptr<base::MessageLoopProxy>& loop,
                          const base::Closure& callback) {
-  if (!loop->BelongsToCurrentThread()) {
+  // The loop.get() check is to support using InProcessCommandBuffer on a thread
+  // without a message loop.
+  if (loop.get() && !loop->BelongsToCurrentThread()) {
     loop->PostTask(FROM_HERE, callback);
   } else {
     callback.Run();
   }
 }
 
 void RunOnTargetThread(scoped_ptr<base::Closure> callback) {
   DCHECK(callback.get());
   callback->Run();
 }
@@ skipping 15 matching lines @@
 
 #if defined(OS_ANDROID)
 scoped_refptr<gfx::SurfaceTexture>
 InProcessCommandBuffer::GetSurfaceTexture(uint32 stream_id) {
   DCHECK(stream_texture_manager_);
   return stream_texture_manager_->GetSurfaceTexture(stream_id);
 }
 #endif
 
 }  // namespace gpu