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

ash/common/system/tray/system_tray_delegate.cc

Index: ash/common/system/tray/system_tray_delegate.cc
diff --git a/ash/common/system/tray/system_tray_delegate.cc b/ash/common/system/tray/system_tray_delegate.cc
index ee83a0f4d4ae45a914b8dec42fc256a893f48ca7..a886d28a92a236c709ff52932c7216454e835852 100644
--- a/ash/common/system/tray/system_tray_delegate.cc
+++ b/ash/common/system/tray/system_tray_delegate.cc
@@ -4,6 +4,8 @@
 
 #include "ash/common/system/tray/system_tray_delegate.h"
 
+#include "ash/common/system/tray/system_tray_item.h"
+
 namespace ash {
 
 NetworkIconInfo::NetworkIconInfo()
@@ -234,4 +236,14 @@ VPNDelegate* SystemTrayDelegate::GetVPNDelegate() const {
   return nullptr;
 }
 
+std::unique_ptr<SystemTrayItem> SystemTrayDelegate::CreateDisplayTrayItem(
+    SystemTray* tray) {
+  return nullptr;
+}
+
+std::unique_ptr<SystemTrayItem> SystemTrayDelegate::CreateRotationLockTrayItem(
+    SystemTray* tray) {
+  return nullptr;
+}
+
 }  // namespace ash