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

mash/task_viewer/task_viewer_application_delegate.h

Index: mash/task_viewer/task_viewer_application_delegate.h
diff --git a/mash/task_viewer/task_viewer_application_delegate.h b/mash/task_viewer/task_viewer_application_delegate.h
index d7f7213cc296b4ba721448488678268a7f725561..efd84c693ef9b84406997ba0afd83d5667c6919a 100644
--- a/mash/task_viewer/task_viewer_application_delegate.h
+++ b/mash/task_viewer/task_viewer_application_delegate.h
@@ -31,7 +31,8 @@ class TaskViewerApplicationDelegate : public mojo::ApplicationDelegate {
 
  private:
   // mojo::ApplicationDelegate:
-  void Initialize(mojo::ApplicationImpl* app) override;
+  void Initialize(mojo::Shell* shell, const std::string& url,
+                  uint32_t id) override;
 
   mojo::TracingImpl tracing_;
   scoped_ptr<views::AuraInit> aura_init_;