gpu: Add CopyTexImage function to GLImage API.

ui/gl/gl_image_stub.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 "ui/gl/gl_image_stub.h"
 
 namespace gfx {
 
 GLImageStub::GLImageStub() {}
 
 GLImageStub::~GLImageStub() {}
 
 gfx::Size GLImageStub::GetSize() { return gfx::Size(1, 1); }
 
 bool GLImageStub::BindTexImage(unsigned target) { return true; }
 
+bool GLImageStub::CopyTexImage(unsigned target) { return true; }
+
 bool GLImageStub::ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                        int z_order,
                                        OverlayTransform transform,
                                        const Rect& bounds_rect,
                                        const RectF& crop_rect) {
   return false;
 }
 
 }  // namespace gfx