Mus: Avoid deadlock during teardown

services/ui/gpu/gpu_main.h

 // 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.
 
 #ifndef SERVICES_UI_GPU_GPU_MAIN_H_
 #define SERVICES_UI_GPU_GPU_MAIN_H_
 
 #include "base/threading/thread.h"
 #include "gpu/ipc/service/gpu_init.h"
 #include "services/ui/gpu/interfaces/gpu_service_internal.mojom.h"
@@ skipping 10 matching lines @@
  public:
   GpuMain();
   ~GpuMain() override;
 
   void OnStart();
   void Create(mojom::GpuServiceInternalRequest request);
 
   GpuServiceInternal* gpu_service() { return gpu_service_internal_.get(); }
 
  private:
-  void InitOnGpuThread();
+  void InitOnGpuThread(
+      scoped_refptr<base::SingleThreadTaskRunner> io_runner,
+      scoped_refptr<base::SingleThreadTaskRunner> compositor_runner);
+
+  void TearDownOnCompositorThread();
   void TearDownOnGpuThread();
   void CreateOnGpuThread(mojom::GpuServiceInternalRequest request);
 
   // gpu::GpuSandboxHelper:
   void PreSandboxStartup() override;
   bool EnsureSandboxInitialized(
       gpu::GpuWatchdogThread* watchdog_thread) override;
 
   std::unique_ptr<gpu::GpuInit> gpu_init_;
   std::unique_ptr<GpuServiceInternal> gpu_service_internal_;
   std::unique_ptr<gpu::GpuMemoryBufferFactory> gpu_memory_buffer_factory_;
 
   // The main thread for GpuService.
   base::Thread gpu_thread_;
 
   // The thread that handles IO events for GpuService.
   base::Thread io_thread_;
 
+  // The thread used for the display compositor.
+  base::Thread compositor_thread_;
+
   base::WeakPtrFactory<GpuMain> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuMain);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_GPU_GPU_MAIN_H_