Use mojo SystemTray interfaces for both mash and classic ash

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 c23c55e3cbe89741035a4fe75ee43b937ac4d52b..346884b182c0a957d027c0ca0db404d46d06826a 100644
--- a/ash/common/system/tray/system_tray_delegate.cc
+++ b/ash/common/system/tray/system_tray_delegate.cc
@@ -77,18 +77,12 @@ void SystemTrayDelegate::GetSystemUpdateInfo(UpdateInfo* info) const {
   info->factory_reset_required = false;
 }
 
-base::HourClockType SystemTrayDelegate::GetHourClockType() const {
-  return base::k24HourClock;
-}
-
 void SystemTrayDelegate::ShowSettings() {}
 
 bool SystemTrayDelegate::ShouldShowSettings() {
   return false;
 }
 
-void SystemTrayDelegate::ShowDateSettings() {}
-
 void SystemTrayDelegate::ShowSetTimeDialog() {}
 
 void SystemTrayDelegate::ShowNetworkSettingsForGuid(const std::string& guid) {}