Add support for EXT_image_flush_external extension

gpu/command_buffer/service/gles2_cmd_decoder_unittest_textures.cc

 // 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.
 
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/command_line.h"
@@ skipping 3011 matching lines @@
                bool(unsigned, const gfx::Point&, const gfx::Rect&));
   MOCK_METHOD5(ScheduleOverlayPlane, bool(gfx::AcceleratedWidget,
                                           int,
                                           gfx::OverlayTransform,
                                           const gfx::Rect&,
                                           const gfx::RectF&));
   MOCK_METHOD3(OnMemoryDump,
                void(base::trace_event::ProcessMemoryDump*,
                     uint64_t,
                     const std::string&));
+  void Flush() override {}
 
  protected:
   virtual ~MockGLImage() {}
 };
 
 TEST_P(GLES2DecoderWithShaderTest, CopyTexImage) {
   DoBindTexture(GL_TEXTURE_2D, client_texture_id_, kServiceTextureId);
   DoTexImage2D(GL_TEXTURE_2D,
                0,
                GL_RGBA,
@@ skipping 849 matching lines @@
 // TODO(gman): CompressedTexSubImage2DImmediate
 
 // TODO(gman): TexImage2D
 
 // TODO(gman): TexImage2DImmediate
 
 // TODO(gman): TexSubImage2DImmediate
 
 }  // namespace gles2
 }  // namespace gpu