mash: Create system tray display and rotation lock items via delegate

ash/common/system/tray/system_tray_delegate.h

Index: ash/common/system/tray/system_tray_delegate.h
diff --git a/ash/common/system/tray/system_tray_delegate.h b/ash/common/system/tray/system_tray_delegate.h
index 5c4de80ebd3808bb956f64740a727d5298067dab..077401a0cdbd1122fd4537a75ef7ba9415aec1ad 100644
--- a/ash/common/system/tray/system_tray_delegate.h
+++ b/ash/common/system/tray/system_tray_delegate.h
@@ -29,6 +29,8 @@ namespace ash {
 
 class CustodianInfoTrayObserver;
 class ShutdownPolicyObserver;
+class SystemTray;
+class SystemTrayItem;
 
 struct ASH_EXPORT NetworkIconInfo {
   NetworkIconInfo();
@@ -335,6 +337,18 @@ class ASH_EXPORT SystemTrayDelegate {
 
   // Returns VPNDelegate. May return nullptr.
   virtual VPNDelegate* GetVPNDelegate() const;
+
+  // Creates a system tray item for display settings.
+  // TODO(jamescook): Remove this when mus has support for display management
+  // and we have a DisplayManager equivalent. See http://crbug.com/548429
+  virtual std::unique_ptr<SystemTrayItem> CreateDisplayTrayItem(
+      SystemTray* tray);
+
+  // Creates a system tray item for display rotation lock.
+  // TODO(jamescook): Remove this when mus has support for display management
+  // and we have a DisplayManager equivalent. See http://crbug.com/548429
+  virtual std::unique_ptr<SystemTrayItem> CreateRotationLockTrayItem(
+      SystemTray* tray);
 };
 
 }  // namespace ash