chrome: Cleanup class/struct forward declarations

chrome/common/extensions/manifest_handlers/linked_app_icons.h

 // Copyright 2015 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_LINKED_APP_ICONS_H_
 #define CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_LINKED_APP_ICONS_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handler.h"
 
-namespace base {
-class DictionaryValue;
-}
-
 namespace extensions {
 
 // A structure to hold the parsed linked app icon data.
 struct LinkedAppIcons : public Extension::ManifestData {
   struct IconInfo {
     IconInfo();
     ~IconInfo();
 
     GURL url;
     int size;
@@ skipping 18 matching lines @@
 
  private:
   const std::vector<std::string> Keys() const override;
 
   DISALLOW_COPY_AND_ASSIGN(LinkedAppIconsHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_LINKED_APP_ICONS_H_