Moves Shell::CreateShelf() to WmShell

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 f92214a0a51b96abe8aaeaee732d75ffff7d186e..6a8f8fd7b7a436c2c1bf2a3f536f90ebeb5e5290 100644
--- a/ash/common/wm_shell.h
+++ b/ash/common/wm_shell.h
@@ -323,6 +323,9 @@ class ASH_EXPORT WmShell {
 
   virtual std::unique_ptr<KeyEventWatcher> CreateKeyEventWatcher() = 0;
 
+  // Initializes the appropriate shelves. Does nothing for any existing shelves.
+  void CreateShelf();
+
   // Show shelf view if it was created hidden (before session has started).
   void ShowShelf();