Added Ash.SystemMenu.DefaultView.VisibleRows histogram.

ash/common/system/cast/tray_cast.cc

Index: ash/common/system/cast/tray_cast.cc
diff --git a/ash/common/system/cast/tray_cast.cc b/ash/common/system/cast/tray_cast.cc
index 4bc171199e30419963aae366baa6d9730094e383..ce21c0eb16be198c1238a31ed9151fdcac6ea217 100644
--- a/ash/common/system/cast/tray_cast.cc
+++ b/ash/common/system/cast/tray_cast.cc
@@ -532,7 +532,8 @@ void CastDetailedView::OnViewClicked(views::View* sender) {
 
 }  // namespace tray
 
-TrayCast::TrayCast(SystemTray* system_tray) : SystemTrayItem(system_tray) {
+TrayCast::TrayCast(SystemTray* system_tray)
+    : SystemTrayItem(system_tray, UMA_CAST) {
   WmShell::Get()->AddShellObserver(this);
 }