Eliminate mojo::Shell client lib class

mash/wm/root_window_controller.h

Index: mash/wm/root_window_controller.h
diff --git a/mash/wm/root_window_controller.h b/mash/wm/root_window_controller.h
index 094e59e70e1822f21f94b3ba1b0b57b92ab41706..2f489b22ab631d67a9e6fbbcca24e207635591ab 100644
--- a/mash/wm/root_window_controller.h
+++ b/mash/wm/root_window_controller.h
@@ -13,7 +13,7 @@
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace mojo {
-class Shell;
+class Connector;
 }
 
 namespace mus {
@@ -48,7 +48,7 @@ class RootWindowController : public mus::WindowObserver,
   // Deletes this.
   void Destroy();
 
-  mojo::Shell* GetShell();
+  mojo::Connector* GetConnector();
 
   mus::Window* root() { return root_; }