Expose GpuMemoryBufferId through glGetImageivCHROMIUM.

gpu/ipc/client/command_buffer_proxy_impl.h

Index: gpu/ipc/client/command_buffer_proxy_impl.h
diff --git a/gpu/ipc/client/command_buffer_proxy_impl.h b/gpu/ipc/client/command_buffer_proxy_impl.h
index c357006ce2a52799eb9c4c8aa4ccb74ab504a8f8..aa47fe30122cd868f30da7916e2b74f374fd7add 100644
--- a/gpu/ipc/client/command_buffer_proxy_impl.h
+++ b/gpu/ipc/client/command_buffer_proxy_impl.h
@@ -123,6 +123,7 @@ class GPU_EXPORT CommandBufferProxyImpl
                                      size_t height,
                                      unsigned internal_format,
                                      unsigned usage) override;
+  int32_t GetImageGpuMemoryBufferId(unsigned image_id) override;
   void SignalQuery(uint32_t query, const base::Closure& callback) override;
   void SetLock(base::Lock* lock) override;
   void EnsureWorkVisible() override;
@@ -295,6 +296,9 @@ class GPU_EXPORT CommandBufferProxyImpl
   SwapBuffersCompletionCallback swap_buffers_completion_callback_;
   UpdateVSyncParametersCallback update_vsync_parameters_completion_callback_;
 
+  // A map from image id to GpuMemoryBuffer id.
+  std::map<int32_t, int32_t> image_gmb_ids_map_;
+
   base::WeakPtr<CommandBufferProxyImpl> weak_this_;
   scoped_refptr<base::SequencedTaskRunner> callback_thread_;