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

mojo/shell/public/cpp/lib/application_delegate.cc

 // 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.
 
 #include "mojo/shell/public/cpp/application_delegate.h"
 
 namespace mojo {
 
 ApplicationDelegate::ApplicationDelegate() {
 }
 ApplicationDelegate::~ApplicationDelegate() {
 }
 
-void ApplicationDelegate::Initialize(ApplicationImpl* app) {
+void ApplicationDelegate::Initialize(Shell* app, const std::string& url,
+                                     uint32_t id) {
 }
 
 bool ApplicationDelegate::AcceptConnection(ApplicationConnection* connection) {
   return true;
 }
 
 bool ApplicationDelegate::ShellConnectionLost() {
   return true;
 }
 
 void ApplicationDelegate::Quit() {
 }
 
 }  // namespace mojo