ios: Cleanup class/struct forward declarations

ios/chrome/browser/share_extension/share_extension_service.h

 // Copyright 2016 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_INTERNAL_CHROME_BROWSER_SHARE_EXTENSION_SHARE_EXTENSION_SERVICE_H_
 #define IOS_INTERNAL_CHROME_BROWSER_SHARE_EXTENSION_SHARE_EXTENSION_SERVICE_H_
 
 #include "components/bookmarks/browser/base_bookmark_model_observer.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/reading_list/ios/reading_list_model_observer.h"
 
 namespace bookmarks {
 class BookmarkModel;
 }
 
-namespace ios {
-class ChromeBrowserState;
-}
-
 class ReadingListModel;
 
 // AuthenticationService is the Chrome interface to the iOS shared
 // authentication library.
 class ShareExtensionService : public KeyedService,
                               public bookmarks::BaseBookmarkModelObserver,
                               public ReadingListModelObserver {
  public:
   explicit ShareExtensionService(bookmarks::BookmarkModel* bookmark_model,
                                  ReadingListModel* reading_list_model);
@@ skipping 12 matching lines @@
 
   ReadingListModel* reading_list_model_;  // not owned.
   bool reading_list_model_loaded_;
   bookmarks::BookmarkModel* bookmark_model_;  // not owned;
   bool bookmark_model_loaded_;
 
   DISALLOW_COPY_AND_ASSIGN(ShareExtensionService);
 };
 
 #endif  // IOS_INTERNAL_CHROME_BROWSER_SHARE_EXTENSION_SHARE_EXTENSION_SERVICE_H_