gpu: Remove Echo and SwapCompletion GL interfacess

gpu/gles2_conform_support/egl/display.cc

 // 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.
 
 #include "gpu/gles2_conform_support/egl/display.h"
 
 #include <vector>
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "gpu/command_buffer/client/gles2_implementation.h"
@@ skipping 296 matching lines @@
 }
 
 void Display::SignalQuery(uint32 query, const base::Closure& callback) {
   NOTIMPLEMENTED();
 }
 
 void Display::SetSurfaceVisible(bool visible) {
   NOTIMPLEMENTED();
 }
 
-void Display::Echo(const base::Closure& callback) {
-  NOTIMPLEMENTED();
-}
-
 uint32 Display::CreateStreamTexture(uint32 texture_id) {
   NOTIMPLEMENTED();
   return 0;
 }
 
 }  // namespace egl