MD system tray: Add user metrics for clicks on the Bluetooth toggle switch.

ash/common/system/chromeos/bluetooth/tray_bluetooth.cc

Index: ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
diff --git a/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc b/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
index ed7284f13a6bf534169ce84bd7248fcd9f954027..6ad8627c428dbc0d52a8b3303e74a458e55bf8b0 100644
--- a/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
+++ b/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
@@ -450,12 +450,17 @@ class BluetoothDetailedView : public TrayDetailsView {
 
   void HandleButtonPressed(views::Button* sender,
                            const ui::Event& event) override {
-    if (sender == toggle_)
-      WmShell::Get()->system_tray_delegate()->ToggleBluetooth();
-    else if (sender == settings_)
+    if (sender == toggle_) {
+      SystemTrayDelegate* delegate = WmShell::Get()->system_tray_delegate();
+      WmShell::Get()->RecordUserMetricsAction(
+          delegate->GetBluetoothEnabled() ? UMA_STATUS_AREA_BLUETOOTH_DISABLED
+                                          : UMA_STATUS_AREA_BLUETOOTH_ENABLED);
+      delegate->ToggleBluetooth();
+    } else if (sender == settings_) {
       ShowSettings();
-    else
+    } else {
       NOTREACHED();
+    }
   }
 
   void CreateExtraTitleRowButtons() override {