Add GpuMemoryBuffer CreateFromClientId interface

gpu/command_buffer/client/gpu_memory_buffer_manager.h

Index: gpu/command_buffer/client/gpu_memory_buffer_manager.h
diff --git a/gpu/command_buffer/client/gpu_memory_buffer_manager.h b/gpu/command_buffer/client/gpu_memory_buffer_manager.h
index 1f56123d03afa51e2752e163cd38470ef4bd7d0f..b6beecdf3fe00bf8bcebf67d4421f18aac090755 100644
--- a/gpu/command_buffer/client/gpu_memory_buffer_manager.h
+++ b/gpu/command_buffer/client/gpu_memory_buffer_manager.h
@@ -33,6 +33,12 @@ class GPU_EXPORT GpuMemoryBufferManager {
       const gfx::Size& size,
       gfx::BufferFormat format) = 0;
 
+  // Creates a new GpuMemoryBuffer instance of a child process' buffer.

[reveman, 2016/05/13 12:28:37]

I don't think we should limit this to child processes. It can be "client" buffer
and the client can potentially be the browser process. The interface is
generally not aware of processes so it's a bit confusing to even mention child
process here.

[ccameron, 2016/05/16 18:41:16]

Ah, good call. Renamed it to just ClientId.

+  virtual std::unique_ptr<gfx::GpuMemoryBuffer>
+  CreateGpuMemoryBufferFromChildId(

[reveman, 2016/05/13 12:28:37]

CreateGpuMemoryBufferFromClientId or just CreateGpuMemoryBufferFromId

[ccameron, 2016/05/16 18:41:16]

Done.

+      int child_client_id,

[reveman, 2016/05/13 12:28:37]

s/child_client_id/client_id/

[ccameron, 2016/05/16 18:41:16]

Done.

+      const gfx::GpuMemoryBufferId& gpu_memory_buffer_id) = 0;
+
   // Returns a GpuMemoryBuffer instance given a ClientBuffer. Returns NULL on
   // failure.
   virtual gfx::GpuMemoryBuffer* GpuMemoryBufferFromClientBuffer(