chrome: Cleanup class/struct forward declarations

chrome/common/extensions/manifest_handlers/settings_overrides_handler.h

 // Copyright 2013 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 CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_SETTINGS_OVERRIDES_HANDLER_H_
 #define CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_SETTINGS_OVERRIDES_HANDLER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "chrome/common/extensions/api/manifest_types.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handler.h"
 
 namespace extensions {
 
 enum SettingsApiOverrideType {
   BUBBLE_TYPE_HOME_PAGE = 0,
   BUBBLE_TYPE_SEARCH_ENGINE,
   BUBBLE_TYPE_STARTUP_PAGES,
 };
 
-class ManifestPermission;
-
 // SettingsOverride is associated with "chrome_settings_overrides" manifest key.
 // An extension can add a search engine as default or non-default, overwrite the
 // homepage and append a startup page to the list.
 struct SettingsOverrides : public Extension::ManifestData {
   SettingsOverrides();
   ~SettingsOverrides() override;
 
   static const SettingsOverrides* Get(const Extension* extension);
 
   std::unique_ptr<api::manifest_types::ChromeSettingsOverrides::Search_provider>
@@ skipping 13 matching lines @@
   bool Parse(Extension* extension, base::string16* error) override;
 
  private:
   const std::vector<std::string> Keys() const override;
 
   DISALLOW_COPY_AND_ASSIGN(SettingsOverridesHandler);
 };
 
 }  // namespace extensions
 #endif  // CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_SETTINGS_OVERRIDES_HANDLER_H_