Fix a crash in mus::GpuService

components/mus/common/gpu_service.cc

 // Copyright 2016 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 "components/mus/common/gpu_service.h"
 
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
+#include "base/threading/thread_restrictions.h"
 #include "components/mus/common/gpu_type_converters.h"
 #include "components/mus/common/mojo_gpu_memory_buffer_manager.h"
 #include "components/mus/common/switches.h"
 #include "components/mus/public/interfaces/gpu_service.mojom.h"
 #include "services/shell/public/cpp/connector.h"
 
 namespace mus {
 
 GpuService::GpuService()
     : main_message_loop_(base::MessageLoop::current()),
@@ skipping 30 matching lines @@
 
   if (gpu_channel_)
     return gpu_channel_;
 
   mus::mojom::GpuServicePtr gpu_service;
   connector->ConnectToInterface("mojo:mus", &gpu_service);
 
   int client_id = 0;
   mojom::ChannelHandlePtr channel_handle;
   mojom::GpuInfoPtr gpu_info;
-  if (!gpu_service->EstablishGpuChannel(&client_id, &channel_handle,
-                                        &gpu_info)) {
-    DLOG(WARNING)
-        << "Channel encountered error while establishing gpu channel.";
-    return nullptr;
+  {
+    // TODO(penghuang): Remove the ScopedAllowWait when HW rendering is enabled
+    // in mus chrome.
+    base::ThreadRestrictions::ScopedAllowWait allow_wait;
+    if (!gpu_service->EstablishGpuChannel(&client_id, &channel_handle,
+                                          &gpu_info)) {
+      DLOG(WARNING)
+          << "Channel encountered error while establishing gpu channel.";
+      return nullptr;
+    }
   }
 
   // TODO(penghuang): Get the real gpu info from mus.
   gpu_channel_ = gpu::GpuChannelHost::Create(
       this, client_id, gpu::GPUInfo(), channel_handle.To<IPC::ChannelHandle>(),
       &shutdown_event_, gpu_memory_buffer_manager_.get());
   return gpu_channel_;
 }
 
 bool GpuService::IsMainThread() {
   return base::MessageLoop::current() == main_message_loop_;
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 GpuService::GetIOThreadTaskRunner() {
   return io_thread_.task_runner();
 }
 
 std::unique_ptr<base::SharedMemory> GpuService::AllocateSharedMemory(
     size_t size) {
   std::unique_ptr<base::SharedMemory> shm(new base::SharedMemory());
   if (!shm->CreateAnonymous(size))
     return std::unique_ptr<base::SharedMemory>();
   return shm;
 }
 
 }  // namespace mus