Replace context parenting by sharing through mailboxes

gpu/ipc/command_buffer_proxy.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_COMMAND_BUFFER_PROXY_H_
 #define GPU_IPC_COMMAND_BUFFER_PROXY_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "gpu/command_buffer/common/command_buffer.h"
 #include "gpu/command_buffer/common/command_buffer_shared.h"
+#include "gpu/command_buffer/common/mailbox.h"
 
 // Client side proxy that forwards messages synchronously to a
 // CommandBufferStub.
 class GPU_EXPORT CommandBufferProxy : public gpu::CommandBuffer {
  public:
   typedef base::Callback<void(
       const std::string& msg, int id)> GpuConsoleMessageCallback;
 
   CommandBufferProxy() { }
 
   virtual ~CommandBufferProxy() { }
 
   virtual int GetRouteID() const = 0;
 
   // Invoke the task when the channel has been flushed. Takes care of deleting
   // the task whether the echo succeeds or not.
   virtual bool Echo(const base::Closure& callback) = 0;
 
-  // 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
-  // and bound as a texture in any other.
-  virtual bool SetParent(CommandBufferProxy* parent_command_buffer,
-                         uint32 parent_texture_id) = 0;
+  // For offscreen contexts, produces the front buffer into a newly created
+  // mailbox.
+  virtual bool ProduceFrontBuffer(const gpu::Mailbox& mailbox) = 0;
 
   virtual void SetChannelErrorCallback(const base::Closure& callback) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CommandBufferProxy);
 };
 
 #endif  // GPU_IPC_COMMAND_BUFFER_PROXY_H_