ios: Cleanup class/struct forward declarations

ios/chrome/browser/favicon/large_icon_cache.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 IOS_CHROME_BROWSER_FAVICON_LARGE_ICON_CACHE_H_
 #define IOS_CHROME_BROWSER_FAVICON_LARGE_ICON_CACHE_H_
 
 #include <memory>
 
 #include "base/containers/mru_cache.h"
 #include "base/macros.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 class GURL;
 struct LargeIconCacheEntry;
 
 namespace favicon_base {
 struct LargeIconResult;
 }
 
-namespace ios {
-class ChromeBrowserState;
-}
-
 // Provides a cache of most recently used LargeIconResult.
 //
 // Example usage:
 //   LargeIconCache* large_icon_cache =
 //       IOSChromeLargeIconServiceFactory::GetForBrowserState(browser_state);
 //   std::unique_ptr<favicon_base::LargeIconResult> icon =
 //       large_icon_cache->GetCachedResult(...);
 //
 class LargeIconCache : public KeyedService {
  public:
@@ skipping 13 matching lines @@
   // Clones a LargeIconResult.
   std::unique_ptr<favicon_base::LargeIconResult> CloneLargeIconResult(
       const favicon_base::LargeIconResult& large_icon_result);
 
   base::MRUCache<GURL, std::unique_ptr<LargeIconCacheEntry>> cache_;
 
   DISALLOW_COPY_AND_ASSIGN(LargeIconCache);
 };
 
 #endif  // IOS_CHROME_BROWSER_FAVICON_LARGE_ICON_CACHE_H_