Allow the renderer process to map textures from one context into another.

content/renderer/gpu/command_buffer_proxy.h

Index: content/renderer/gpu/command_buffer_proxy.h
===================================================================
--- content/renderer/gpu/command_buffer_proxy.h	(revision 94701)
+++ content/renderer/gpu/command_buffer_proxy.h	(working copy)
@@ -15,6 +15,7 @@
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/renderer/gpu/gpu_video_decode_accelerator_host.h"
+#include "gpu/command_buffer/common/constants.h"
 #include "gpu/command_buffer/common/command_buffer.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_message.h"
@@ -64,6 +65,11 @@
   virtual void SetContextLostReason(gpu::error::ContextLostReason reason);
   virtual void OnSwapBuffers();
 
+  bool MapExternalResource(gpu::resource_type::ResourceType resource_type,
+                           uint32 resource_source_id,
+                           CommandBufferProxy* source_command_buffer,
+                           uint32 resource_dest_id);
+
   // Reparent a command buffer. TODO(apatrick): going forward, the notion of
   // the parent / child relationship between command buffers is going away in
   // favor of the notion of surfaces that can be drawn to in one command buffer