mash: Remove StatusAreaWidget references from system tray classes

ash/system/chromeos/virtual_keyboard/virtual_keyboard_tray.h

Index: ash/system/chromeos/virtual_keyboard/virtual_keyboard_tray.h
diff --git a/ash/system/chromeos/virtual_keyboard/virtual_keyboard_tray.h b/ash/system/chromeos/virtual_keyboard/virtual_keyboard_tray.h
index 363a59b1c193e609fe63379f7e3f06ce3cf0218f..3dadedff592d7801d74866d64ee9a55ffd4eadbf 100644
--- a/ash/system/chromeos/virtual_keyboard/virtual_keyboard_tray.h
+++ b/ash/system/chromeos/virtual_keyboard/virtual_keyboard_tray.h
@@ -15,14 +15,15 @@ class ImageButton;
 }
 
 namespace ash {
-class StatusAreaWidget;
+
+class WmShelf;
 
 // TODO(sky): make this visible on non-chromeos platforms.
 class VirtualKeyboardTray : public TrayBackgroundView,
                             public views::ButtonListener,
                             public KeyboardUIObserver {
  public:
-  explicit VirtualKeyboardTray(StatusAreaWidget* status_area_widget);
+  explicit VirtualKeyboardTray(WmShelf* wm_shelf);
   ~VirtualKeyboardTray() override;
 
   // TrayBackgroundView: