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

ash/system/tray/system_tray.cc

Index: ash/system/tray/system_tray.cc
diff --git a/ash/system/tray/system_tray.cc b/ash/system/tray/system_tray.cc
index b9b8141f17e0e7eb8021c01f73d1a188fc9a1505..f24a7a13396d42fb27441862eb21382db3ef75b4 100644
--- a/ash/system/tray/system_tray.cc
+++ b/ash/system/tray/system_tray.cc
@@ -197,7 +197,10 @@ void SystemTray::CreateItems(SystemTrayDelegate* delegate) {
   AddTrayItem(new TrayBluetooth(this));
   tray_cast_ = new TrayCast(this);
   AddTrayItem(tray_cast_);
-  AddTrayItem(new TrayDisplay(this));
+  std::unique_ptr<SystemTrayItem> tray_display =

[msw, 2016/07/13 18:51:49]

optional nit: add a comment?

[James Cook, 2016/07/13 21:30:46]

Done.

+      delegate->CreateDisplayTrayItem(this);
+  if (tray_display)
+    AddTrayItem(tray_display.release());
   screen_capture_tray_item_ = new ScreenCaptureTrayItem(this);
   AddTrayItem(screen_capture_tray_item_);
   screen_share_tray_item_ = new ScreenShareTrayItem(this);
@@ -233,10 +236,6 @@ void SystemTray::AddTrayItem(SystemTrayItem* item) {
   }
 }
 
-void SystemTray::RemoveTrayItem(SystemTrayItem* item) {
-  NOTIMPLEMENTED();
-}
-
 const std::vector<SystemTrayItem*>& SystemTray::GetTrayItems() const {
   return items_.get();
 }