Add palette tray to ash.

ash/common/system/status_area_widget.h

Index: ash/common/system/status_area_widget.h
diff --git a/ash/common/system/status_area_widget.h b/ash/common/system/status_area_widget.h
index 8fa40c4a11d0f143a652930f412f47cfa6a08e31..8cad28aea138ecff9a6d5aa64403e7e5671e9546 100644
--- a/ash/common/system/status_area_widget.h
+++ b/ash/common/system/status_area_widget.h
@@ -21,6 +21,7 @@ class WmShelf;
 class WmWindow;
 #if defined(OS_CHROMEOS)
 class LogoutButtonTray;
+class PaletteTray;
 class VirtualKeyboardTray;
 #endif
 
@@ -78,6 +79,7 @@ class ASH_EXPORT StatusAreaWidget : public views::Widget {
   void AddWebNotificationTray();
 #if defined(OS_CHROMEOS)
   void AddLogoutButtonTray();
+  void AddPaletteTray();
   void AddVirtualKeyboardTray();
 #endif
   void AddOverviewButtonTray();
@@ -89,6 +91,7 @@ class ASH_EXPORT StatusAreaWidget : public views::Widget {
   WebNotificationTray* web_notification_tray_;
 #if defined(OS_CHROMEOS)
   LogoutButtonTray* logout_button_tray_;
+  PaletteTray* palette_tray_;
   VirtualKeyboardTray* virtual_keyboard_tray_;
 #endif
   LoginStatus login_status_;