Remove extension group from DOMWrapperWorld.

extensions/renderer/extension_groups.h

-// 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.
-
-#ifndef EXTENSIONS_RENDERER_EXTENSION_GROUPS_H_
-#define EXTENSIONS_RENDERER_EXTENSION_GROUPS_H_
-
-namespace extensions {
-
-// A set of extension groups for use with blink::registerExtension and
-// WebFrame::ExecuteScriptInNewWorld to control which extensions get loaded
-// into which contexts.
-// TODO(kalman): Remove this when https://crbug.com/481699 is fixed.
-enum ExtensionGroups {
-  // Use this to mark extensions to be loaded into content scripts only.
-  EXTENSION_GROUP_CONTENT_SCRIPTS = 1,
-};
-
-}  // namespace extensions
-
-#endif  // EXTENSIONS_RENDERER_EXTENSION_GROUPS_H_