chrome: Cleanup class/struct forward declarations

chrome/common/extensions/manifest_handlers/app_icon_color_info.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 CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_APP_ICON_COLOR_INFO_H_
 #define CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_APP_ICON_COLOR_INFO_H_
 
 #include "base/macros.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handler.h"
 #include "third_party/skia/include/core/SkColor.h"
 
-namespace base {
-class DictionaryValue;
-}
-
 namespace extensions {
 
 // A structure to hold the parsed app icon color data.
 struct AppIconColorInfo : public Extension::ManifestData {
   AppIconColorInfo();
   ~AppIconColorInfo() override;
 
   static SkColor GetIconColor(const Extension* extension);
   static const std::string& GetIconColorString(const Extension* extension);
 
@@ skipping 14 matching lines @@
 
  private:
   const std::vector<std::string> Keys() const override;
 
   DISALLOW_COPY_AND_ASSIGN(AppIconColorHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_MANIFEST_HANDLERS_APP_ICON_COLOR_INFO_H_