Extract shell methods from ApplicationImpl into a base class, and pass this to Initialize() instead.

components/html_viewer/html_frame_delegate.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 COMPONENTS_HTML_VIEWER_HTML_FRAME_DELEGATE_H_
 #define COMPONENTS_HTML_VIEWER_HTML_FRAME_DELEGATE_H_
 
 namespace mojo {
-class ApplicationImpl;
+class Shell;
 }
 
 namespace html_viewer {
 
 class HTMLFactory;
 class HTMLFrame;
 
 class HTMLFrameDelegate {
  public:
-  // Returns the ApplicationImpl for the frame.
-  virtual mojo::ApplicationImpl* GetApp() = 0;
+  // Returns the Shell for the frame.
+  virtual mojo::Shell* GetShell() = 0;
 
   // Returns the factory for creating various classes.
   virtual HTMLFactory* GetHTMLFactory() = 0;
 
   // Invoked when the Frame the delegate is attached to finishes loading. This
   // is not invoked for any child frames, only the frame returned from
   // HTMLFrameTreeManager::CreateFrameAndAttachToTree().
   virtual void OnFrameDidFinishLoad() = 0;
 
   // Invoked when the HTMLFrame the delegate is associated with is swapped
   // to a remote frame.
   virtual void OnFrameSwappedToRemote() = 0;
 
   // Invoked when this delegate is to take over from |old_delegate| (which may
   // be null). This is invoked when a new connection is established and we
   // are already rendering to the supplied frame.
   virtual void OnSwap(HTMLFrame* frame, HTMLFrameDelegate* old_delegate) = 0;
 
   // Invoked when the HTMLFrame is destroyed.
   virtual void OnFrameDestroyed() = 0;
 
  protected:
   virtual ~HTMLFrameDelegate() {}
 };
 
 }  // namespace html_viewer
 
 #endif  // COMPONENTS_HTML_VIEWER_HTML_FRAME_DELEGATE_H_