mash: Port context menu code to WmShell and WmRootWindowController.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 1f4623333a5713917f1b4d6b1223d850279b0903..bc902c531780f3ac561f6cf0aa9ecbd78af6a19c 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -19,7 +19,6 @@
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "ui/aura/window.h"
-#include "ui/base/ui_base_types.h"
 #include "ui/display/screen.h"
 #include "ui/events/event_target.h"
 #include "ui/gfx/geometry/insets.h"
@@ -42,7 +41,6 @@ class AudioA11yController;
 
 namespace gfx {
 class ImageSkia;
-class Point;
 class Rect;
 }
 
@@ -192,10 +190,6 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   static const aura::Window* GetContainer(const aura::Window* root_window,
                                           int container_id);
 
-  // Shows the context menu for the wallpaper and shelf at the screen location.
-  void ShowContextMenu(const gfx::Point& location_in_screen,
-                       ui::MenuSourceType source_type);
-
   // Creates a default views::NonClientFrameView for use by windows in the
   // Ash environment.
   views::NonClientFrameView* CreateDefaultNonClientFrameView(