Add a11y virtual keyboard icon when a11y VK is enabled

ash/system/status_area_widget.h

Index: ash/system/status_area_widget.h
diff --git a/ash/system/status_area_widget.h b/ash/system/status_area_widget.h
index 7aa2bc7423f7bb486bf11a2a21b9c5e919ab69f9..9933c73f2c9e7aae089ac03592e475930fb3d766 100644
--- a/ash/system/status_area_widget.h
+++ b/ash/system/status_area_widget.h
@@ -20,6 +20,9 @@ namespace internal {
 
 class LogoutButtonTray;
 class StatusAreaWidgetDelegate;
+#if defined(OS_CHROMEOS)
+class VirtualKeyboardTray;
+#endif
 
 class ASH_EXPORT StatusAreaWidget : public views::Widget {
  public:
@@ -71,12 +74,18 @@ class ASH_EXPORT StatusAreaWidget : public views::Widget {
   void AddSystemTray();
   void AddWebNotificationTray();
   void AddLogoutButtonTray();
+#if defined(OS_CHROMEOS)
+  void AddVirtualKeyboardTray();
+#endif
 
   // Weak pointers to View classes that are parented to StatusAreaWidget:
   internal::StatusAreaWidgetDelegate* status_area_widget_delegate_;
   SystemTray* system_tray_;
   WebNotificationTray* web_notification_tray_;
   LogoutButtonTray* logout_button_tray_;
+#if defined(OS_CHROMEOS)
+  VirtualKeyboardTray* virtual_keyboard_tray_;
+#endif
   user::LoginStatus login_status_;
 
   DISALLOW_COPY_AND_ASSIGN(StatusAreaWidget);