gpu: Add CopyTexImage function to GLImage API.

ui/gl/gl_image_stub.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 UI_GL_GL_IMAGE_STUB_H_
 #define UI_GL_GL_IMAGE_STUB_H_
 
 #include "ui/gl/gl_image.h"
 
 namespace gfx {
 
 // A GLImage that does nothing for unit tests.
 class GL_EXPORT GLImageStub : public GLImage {
  public:
   GLImageStub();
 
   // Overridden from GLImage:
   virtual void Destroy(bool have_context) OVERRIDE {}
   virtual gfx::Size GetSize() OVERRIDE;
   virtual bool BindTexImage(unsigned target) OVERRIDE;
   virtual void ReleaseTexImage(unsigned target) OVERRIDE {}
+  virtual bool CopyTexImage(unsigned target) OVERRIDE;
   virtual void WillUseTexImage() OVERRIDE {}
   virtual void DidUseTexImage() OVERRIDE {}
   virtual void WillModifyTexImage() OVERRIDE {}
   virtual void DidModifyTexImage() OVERRIDE {}
   virtual bool ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                     int z_order,
                                     OverlayTransform transform,
                                     const Rect& bounds_rect,
                                     const RectF& crop_rect) OVERRIDE;
 
  protected:
   virtual ~GLImageStub();
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_IMAGE_STUB_H_