CommandBufferProxyImpl holds on to GpuMemoryBuffers while they are in use.

gpu/ipc/client/command_buffer_proxy_impl.h

 // Copyright (c) 2012 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 GPU_IPC_CLIENT_COMMAND_BUFFER_PROXY_IMPL_H_
 #define GPU_IPC_CLIENT_COMMAND_BUFFER_PROXY_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 281 matching lines @@
   gpu::Capabilities capabilities_;
 
   std::vector<ui::LatencyInfo> latency_info_;
 
   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_;
 
+  // A map of GpuMemoryBuffers owned by this class (created from
+  // CreateGpuMemoryBufferImage). Unfortunatley, this cannot be combined with
+  // |image_gmb_ids_map_| since that container does not imply ownership.

[piman, 2016/06/06 19:28:52]

nit: would it be possible to combine both maps, by having a move-only struct
that has both the GMB id and the unique_ptr?
struct ImageInfo {
  int32_t gpu_memory_buffer_id;
  std::unique_ptr<gfx::GpuMemoryBuffer> owned_gpu_memory_buffer;
};

Otherwise, can you mention that the index is the image id as well (not clear
here).

[erikchen, 2016/06/06 21:55:54]

I created the ImageInfo struct as you suggested.

+  std::map<int32_t, std::unique_ptr<gfx::GpuMemoryBuffer>> image_gmb_map_;
+
   base::WeakPtr<CommandBufferProxyImpl> weak_this_;
   scoped_refptr<base::SequencedTaskRunner> callback_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(CommandBufferProxyImpl);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_IPC_CLIENT_COMMAND_BUFFER_PROXY_IMPL_H_