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

components/mus/public/cpp/window_tree_connection.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 COMPONENTS_MUS_PUBLIC_CPP_WINDOW_TREE_CONNECTION_H_
 #define COMPONENTS_MUS_PUBLIC_CPP_WINDOW_TREE_CONNECTION_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "components/mus/common/types.h"
 #include "components/mus/public/interfaces/window_tree.mojom.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 
 namespace mojo {
-class ApplicationImpl;
+class Shell;
 }
 
 namespace mus {
 
 class Window;
 class WindowManagerDelegate;
 class WindowTreeConnectionObserver;
 class WindowTreeDelegate;
 
 // Encapsulates a connection to a window tree. A unique connection is made
 // every time an app is embedded.
 class WindowTreeConnection {
  public:
   enum class CreateType {
     // Indicates Create() should wait for OnEmbed(). If true, the
     // WindowTreeConnection returned from Create() will have its root, otherwise
     // the WindowTreeConnection will get the root at a later time.
     WAIT_FOR_EMBED,
     DONT_WAIT_FOR_EMBED
   };
 
   virtual ~WindowTreeConnection() {}
 
   // Creates a WindowTreeConnection with no roots. Use this to establish a
   // connection directly to mus and create top level windows.
   static WindowTreeConnection* Create(WindowTreeDelegate* delegate,
-                                      mojo::ApplicationImpl* app);
+                                      mojo::Shell* shell);
 
   // Creates a WindowTreeConnection to service the specified request for
   // a WindowTreeClient. Use this to be embedded in another app.
   static WindowTreeConnection* Create(
       WindowTreeDelegate* delegate,
       mojo::InterfaceRequest<mojom::WindowTreeClient> request,
       CreateType create_type);
 
   // Create a WindowTreeConnection that is going to serve as the WindowManager.
   static WindowTreeConnection* CreateForWindowManager(
@@ skipping 31 matching lines @@
   // TODO(sky): remove this. It is not necessarily correct anymore.
   virtual ConnectionSpecificId GetConnectionId() = 0;
 
   virtual void AddObserver(WindowTreeConnectionObserver* observer) = 0;
   virtual void RemoveObserver(WindowTreeConnectionObserver* observer) = 0;
 };
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_PUBLIC_CPP_WINDOW_TREE_CONNECTION_H_