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

mandoline/ui/desktop_ui/browser_window.h

Index: mandoline/ui/desktop_ui/browser_window.h
diff --git a/mandoline/ui/desktop_ui/browser_window.h b/mandoline/ui/desktop_ui/browser_window.h
index 67e21949ebe22bbe960b31f27248ce77ad416226..31d188058d46596a2c1e747d61750dfdb1cb9108 100644
--- a/mandoline/ui/desktop_ui/browser_window.h
+++ b/mandoline/ui/desktop_ui/browser_window.h
@@ -51,7 +51,7 @@ class BrowserWindow : public mus::WindowTreeDelegate,
                       public FindBarDelegate,
                       public mus::WindowManagerDelegate {
  public:
-  BrowserWindow(mojo::ApplicationImpl* app,
+  BrowserWindow(mojo::Shell* shell,
                 mus::mojom::WindowTreeHostFactory* host_factory,
                 BrowserManager* manager);
 
@@ -114,7 +114,7 @@ class BrowserWindow : public mus::WindowTreeDelegate,
 
   void Layout(views::View* host);
 
-  mojo::ApplicationImpl* app_;
+  mojo::Shell* shell_;
   mus::WindowManagerClient* window_manager_client_;
   scoped_ptr<ui::mojo::UIInit> ui_init_;
   scoped_ptr<views::AuraInit> aura_init_;