chrome: Cleanup class/struct forward declarations

chrome/browser/ui/cocoa/handoff_active_url_observer.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_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_H_
 #define CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_H_
 
 #include "base/macros.h"
 #include "chrome/browser/ui/browser_list_observer.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
 #include "content/public/browser/web_contents_observer.h"
 
 namespace content {
 class WebContents;
 }
 
 class Browser;
 class HandoffActiveURLObserverDelegate;
-class TabStripModel;
 
 // This class observes changes to the "active URL". This is defined as the
 // visible URL of the WebContents of the selected tab of the most recently
 // focused browser window.
 class HandoffActiveURLObserver : public chrome::BrowserListObserver,
                                  public TabStripModelObserver,
                                  public content::WebContentsObserver {
  public:
   explicit HandoffActiveURLObserver(HandoffActiveURLObserverDelegate* delegate);
   ~HandoffActiveURLObserver() override;
@@ skipping 31 matching lines @@
   HandoffActiveURLObserverDelegate* delegate_;
 
   // This pointer is always up to date, and points to the most recently
   // activated browser, or nullptr if no browsers exist.
   Browser* active_browser_;
 
   DISALLOW_COPY_AND_ASSIGN(HandoffActiveURLObserver);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_HANDOFF_ACTIVE_URL_OBSERVER_H_