chrome: Cleanup class/struct forward declarations

chrome/common/extensions/chrome_manifest_url_handlers.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 CHROME_COMMON_EXTENSIONS_CHROME_MANIFEST_URL_HANDLERS_H_
 #define CHROME_COMMON_EXTENSIONS_CHROME_MANIFEST_URL_HANDLERS_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handler.h"
 
 // Chrome-specific extension manifest URL handlers.
 
-namespace base {
-class DictionaryValue;
-}
-
 namespace extensions {
 
 namespace chrome_manifest_urls {
 const GURL& GetDevToolsPage(const Extension* extension);
 }
 
 // Stores Chrome URL overrides specified in extensions manifests.
 struct URLOverrides : public Extension::ManifestData {
   typedef std::map<const std::string, GURL> URLOverrideMap;
 
@@ skipping 35 matching lines @@
 
  private:
   const std::vector<std::string> Keys() const override;
 
   DISALLOW_COPY_AND_ASSIGN(URLOverridesHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_CHROME_MANIFEST_URL_HANDLERS_H_