Refactor so chromium only GL extensions require gl2extchromium.h

gpu/command_buffer/tests/gl_copy_texture_CHROMIUM_unittest.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.
 
 #ifndef GL_GLEXT_PROTOTYPES
 #define GL_GLEXT_PROTOTYPES
 #endif
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
+#include <GLES2/gl2extchromium.h>
 
 #include "gpu/command_buffer/tests/gl_manager.h"
 #include "gpu/command_buffer/tests/gl_test_utils.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace gpu {
 
 // A collection of tests that exercise the GL_CHROMIUM_copy_texture extension.
 class GLCopyTextureCHROMIUMTest : public testing::Test {
@@ skipping 442 matching lines @@
   EXPECT_TRUE(GLTestHelper::CheckPixels(0, 0, 1, 1, 0, expected));
 
   EXPECT_TRUE(GL_NO_ERROR == glGetError());
 
   gl2.MakeCurrent();
   gl2.Destroy();
   gl_.MakeCurrent();
 }
 
 }  // namespace gpu