[Chrome OS MD] Draw a 1px separator between 2 tray items

ash/mus/bridge/wm_shelf_mus.cc

Index: ash/mus/bridge/wm_shelf_mus.cc
diff --git a/ash/mus/bridge/wm_shelf_mus.cc b/ash/mus/bridge/wm_shelf_mus.cc
index f56328c73c76dbb7467176f370b1499ed7d495b4..0ae741bf7ed6f5c07748a42dc17c48305735d523 100644
--- a/ash/mus/bridge/wm_shelf_mus.cc
+++ b/ash/mus/bridge/wm_shelf_mus.cc
@@ -129,6 +129,11 @@ void WmShelfMus::RemoveObserver(WmShelfObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+StatusAreaWidget* WmShelfMus::GetStatusAreaWidget() {
+  NOTIMPLEMENTED();
+  return nullptr;
+}
+
 void WmShelfMus::SetKeyboardBoundsForTesting(const gfx::Rect& bounds) {
   NOTIMPLEMENTED();
 }