Fix potential shutdown deadlock in UI service

services/ui/public/cpp/gpu/client_gpu_memory_buffer_manager.h

 // Copyright 2015 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_PUBLIC_CPP_GPU_CLIENT_GPU_MEMORY_BUFFER_MANAGER_H_
 #define SERVICES_UI_PUBLIC_CPP_GPU_CLIENT_GPU_MEMORY_BUFFER_MANAGER_H_
 
 #include <memory>
+#include <set>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread.h"
 #include "gpu/command_buffer/client/gpu_memory_buffer_manager.h"
 #include "services/ui/public/interfaces/gpu.mojom.h"
 
 namespace base {
 class WaitableEvent;
 }
 
 namespace ui {
 
 class ClientGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager {
  public:
   explicit ClientGpuMemoryBufferManager(mojom::GpuPtr gpu);
   ~ClientGpuMemoryBufferManager() override;
 
  private:
   void InitThread(mojom::GpuPtrInfo gpu_info);
   void TearDownThread();
+  void DisconnectGpuOnThread();
   void AllocateGpuMemoryBufferOnThread(const gfx::Size& size,
                                        gfx::BufferFormat format,
                                        gfx::BufferUsage usage,
                                        gfx::GpuMemoryBufferHandle* handle,
                                        base::WaitableEvent* wait);
+  void OnGpuMemoryBufferAllocatedOnThread(
+      gfx::GpuMemoryBufferHandle* ret_handle,
+      base::WaitableEvent* wait,
+      const gfx::GpuMemoryBufferHandle& handle);
   void DeletedGpuMemoryBuffer(gfx::GpuMemoryBufferId id,
                               const gpu::SyncToken& sync_token);
 
   // Overridden from gpu::GpuMemoryBufferManager:
   std::unique_ptr<gfx::GpuMemoryBuffer> CreateGpuMemoryBuffer(
       const gfx::Size& size,
       gfx::BufferFormat format,
       gfx::BufferUsage usage,
       gpu::SurfaceHandle surface_handle) override;
   void SetDestructionSyncToken(gfx::GpuMemoryBuffer* buffer,
                                const gpu::SyncToken& sync_token) override;
+
   int counter_ = 0;
   // TODO(sad): Explore the option of doing this from an existing thread.
   base::Thread thread_;
   mojom::GpuPtr gpu_;
   base::WeakPtr<ClientGpuMemoryBufferManager> weak_ptr_;
+  std::set<base::WaitableEvent*> pending_allocation_waiters_;
   base::WeakPtrFactory<ClientGpuMemoryBufferManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ClientGpuMemoryBufferManager);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_GPU_CLIENT_GPU_MEMORY_BUFFER_MANAGER_H_