gpu: Remove Echo and SwapCompletion GL interfacess

gpu/command_buffer/client/gpu_control.h

 // Copyright 2014 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_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_
 #define GPU_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 46 matching lines @@
   // Runs |callback| when a sync point is reached.
   virtual void SignalSyncPoint(uint32_t sync_point,
                                const base::Closure& callback) = 0;
 
   // Runs |callback| when a query created via glCreateQueryEXT() has cleared
   // passed the glEndQueryEXT() point.
   virtual void SignalQuery(uint32_t query, const base::Closure& callback) = 0;
 
   virtual void SetSurfaceVisible(bool visible) = 0;
 
-  // Invokes the callback once the context has been flushed.
-  virtual void Echo(const base::Closure& callback) = 0;
-
   // Attaches an external stream to the texture given by |texture_id| and
   // returns a stream identifier.
   virtual uint32_t CreateStreamTexture(uint32_t texture_id) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GpuControl);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_