mus: Simplify generation of memory-buffer ids.

services/ui/common/mus_gpu_memory_buffer_manager.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_COMMON_MUS_GPU_MEMORY_BUFFER_MANAGER_H_
 #define SERVICES_UI_COMMON_MUS_GPU_MEMORY_BUFFER_MANAGER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
 #include "gpu/command_buffer/client/gpu_memory_buffer_manager.h"
 #include "services/ui/gpu/interfaces/gpu_service_internal.mojom.h"
 
 namespace ui {
 
 // This GpuMemoryBufferManager is for establishing a GpuChannelHost used by
 // mus locally.
-class MusGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager {
+class MusGpuMemoryBufferManager : public gpu::GpuMemoryBufferManager,
+                                  public base::ThreadChecker {
  public:
   MusGpuMemoryBufferManager(mojom::GpuServiceInternal* gpu_service,
                             int client_id);
   ~MusGpuMemoryBufferManager() override;
 
   // 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;
   std::unique_ptr<gfx::GpuMemoryBuffer> CreateGpuMemoryBufferFromHandle(
       const gfx::GpuMemoryBufferHandle& handle,
       const gfx::Size& size,
       gfx::BufferFormat format) override;
   void SetDestructionSyncToken(gfx::GpuMemoryBuffer* buffer,
                                const gpu::SyncToken& sync_token) override;
 
  private:
   void DestroyGpuMemoryBuffer(gfx::GpuMemoryBufferId id,
                               int client_id,
                               bool is_native,
                               const gpu::SyncToken& sync_token);
 
   mojom::GpuServiceInternal* gpu_service_;
 
   const int client_id_;
+  int next_gpu_memory_id_ = 1;
   base::WeakPtrFactory<MusGpuMemoryBufferManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MusGpuMemoryBufferManager);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_COMMON_MUS_GPU_MEMORY_BUFFER_MANAGER_H_