mash: Create and show a shelf in mash.

ash/common/wm_shell.h

Index: ash/common/wm_shell.h
diff --git a/ash/common/wm_shell.h b/ash/common/wm_shell.h
index c064efded59347fd85c8fb0c3df29546c5ca8f04..794c516fb0c4cd99dab25abcad2f8972d8a4d0af 100644
--- a/ash/common/wm_shell.h
+++ b/ash/common/wm_shell.h
@@ -269,6 +269,8 @@ class ASH_EXPORT WmShell {
   virtual std::unique_ptr<WmImmersiveFullscreenController>
   CreateImmersiveFullscreenController() = 0;
 
+  void CreateShelfDelegate();
+
   // Called after maximize mode has started, windows might still animate though.
   void OnMaximizeModeStarted();
 
@@ -356,8 +358,6 @@ class ASH_EXPORT WmShell {
   void SetSystemTrayDelegate(std::unique_ptr<SystemTrayDelegate> delegate);
   void DeleteSystemTrayDelegate();
 
-  void CreateShelfDelegate();
-
   void DeleteWindowCycleController();
 
   void DeleteWindowSelectorController();