ios: Cleanup class/struct forward declarations

ios/web/navigation/navigation_item_facade_delegate.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 IOS_WEB_NAVIGATION_NAVIGATION_ITEM_FACADE_DELEGATE_H_
 #define IOS_WEB_NAVIGATION_NAVIGATION_ITEM_FACADE_DELEGATE_H_
 
 namespace content {
 class NavigationEntry;
 }
 
 namespace web {
 
-class NavigationItemImpl;
-
 // Interface used by NavigationItems to interact with their NavigationEntry
 // facades.  This pushes references to NavigationEntry out of the web-layer.
 // Note that since communication is one-directional, this interface is primarily
 // to add hooks for creation/deletion of facades.
 class NavigationItemFacadeDelegate {
  public:
   NavigationItemFacadeDelegate() {}
   virtual ~NavigationItemFacadeDelegate() {}
 
   // Returns the facade object being driven by this delegate.
   virtual content::NavigationEntry* GetNavigationEntryFacade() = 0;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_NAVIGATION_NAVIGATION_ITEM_FACADE_DELEGATE_H_