Added Ash.SystemMenu.DefaultView.VisibleRows histogram.

ash/system/chromeos/bluetooth/tray_bluetooth.cc

Index: ash/system/chromeos/bluetooth/tray_bluetooth.cc
diff --git a/ash/system/chromeos/bluetooth/tray_bluetooth.cc b/ash/system/chromeos/bluetooth/tray_bluetooth.cc
index 9a1bd2031e2745ec774cc41ea5fa0970a2149b62..7875a0b0860443fc2f1566ad1f7292eb30ba73da 100644
--- a/ash/system/chromeos/bluetooth/tray_bluetooth.cc
+++ b/ash/system/chromeos/bluetooth/tray_bluetooth.cc
@@ -394,7 +394,9 @@ class BluetoothDetailedView : public TrayDetailsView,
 }  // namespace tray
 
 TrayBluetooth::TrayBluetooth(SystemTray* system_tray)
-    : SystemTrayItem(system_tray), default_(NULL), detailed_(NULL) {
+    : SystemTrayItem(system_tray, UMA_BLUETOOTH),
+      default_(NULL),
+      detailed_(NULL) {
   WmShell::Get()->system_tray_notifier()->AddBluetoothObserver(this);
 }