ui: Cleanup class/struct forward declarations

chrome/browser/ui/views/javascript_app_modal_event_blocker_x11.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_VIEWS_JAVASCRIPT_APP_MODAL_EVENT_BLOCKER_X11_H_
 #define CHROME_BROWSER_UI_VIEWS_JAVASCRIPT_APP_MODAL_EVENT_BLOCKER_X11_H_
 
 #include "base/macros.h"
 #include "ui/events/event_handler.h"
 
 class BrowserView;
 
 namespace aura {
 class Window;
 }
 
+namespace ui {
+class EventTarget;
+}
+
 // JavascriptAppModalEventBlockerX11 blocks events to all browser windows except
 // the browser window which hosts |app_modal_window| for the duration of its
 // lifetime. JavascriptAppModalEventBlockerX11 should not outlive
 // |app_modal_window|.
 // TODO(pkotwicz): Merge this class into WindowModalityController.
 class JavascriptAppModalEventBlockerX11 : public ui::EventHandler {
  public:
   explicit JavascriptAppModalEventBlockerX11(aura::Window* app_modal_window);
   ~JavascriptAppModalEventBlockerX11() override;
 
@@ skipping 10 matching lines @@
   // The app modal dialog.
   aura::Window* modal_window_;
 
   // The BrowserView which hosts the app modal dialog.
   BrowserView* browser_view_with_modal_dialog_;
 
   DISALLOW_COPY_AND_ASSIGN(JavascriptAppModalEventBlockerX11);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_JAVASCRIPT_APP_MODAL_EVENT_BLOCKER_X11_H_