ios: Cleanup class/struct forward declarations

ios/chrome/browser/bookmarks/bookmark_client_impl.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_BOOKMARKS_BOOKMARK_CLIENT_IMPL_H_
 #define IOS_CHROME_BROWSER_BOOKMARKS_BOOKMARK_CLIENT_IMPL_H_
 
 #include <set>
 #include <vector>
 
 #include "base/deferred_sequenced_task_runner.h"
 #include "base/macros.h"
 #include "components/bookmarks/browser/bookmark_client.h"
 
 class GURL;
 
-namespace base {
-class ListValue;
-}
-
 namespace bookmarks {
-class BookmarkModel;
 class BookmarkNode;
 class BookmarkPermanentNode;
 }
 
 namespace ios {
 class ChromeBrowserState;
 }
 
 class BookmarkClientImpl : public bookmarks::BookmarkClient {
  public:
@@ skipping 22 matching lines @@
 
  private:
   // Pointer to the associated ios::ChromeBrowserState. Must outlive
   // BookmarkClientImpl.
   ios::ChromeBrowserState* browser_state_;
 
   DISALLOW_COPY_AND_ASSIGN(BookmarkClientImpl);
 };
 
 #endif  // IOS_CHROME_BROWSER_BOOKMARKS_BOOKMARK_CLIENT_IMPL_H_