Added class BluetoothDeviceMac, returns mac device timing data

device/bluetooth/bluetooth_low_energy_device_mac.mm

Index: device/bluetooth/bluetooth_low_energy_device_mac.mm
diff --git a/device/bluetooth/bluetooth_low_energy_device_mac.mm b/device/bluetooth/bluetooth_low_energy_device_mac.mm
index 0357ad95276aca951b3d3a10d7032ff4c230c32f..cd2823c8a02d030c877d948d7ab7dcc88c747c78 100644
--- a/device/bluetooth/bluetooth_low_energy_device_mac.mm
+++ b/device/bluetooth/bluetooth_low_energy_device_mac.mm
@@ -75,6 +75,7 @@ BluetoothLowEnergyDeviceMac::~BluetoothLowEnergyDeviceMac() {
 void BluetoothLowEnergyDeviceMac::Update(CBPeripheral* peripheral,
                                          NSDictionary* advertisementData,
                                          int rssi) {
+  last_update_time_.reset([[NSDate date] retain]);
   peripheral_.reset([peripheral retain]);
   rssi_ = rssi;
   ClearServiceData();
@@ -226,6 +227,10 @@ void BluetoothLowEnergyDeviceMac::CreateGattConnection(
   NOTIMPLEMENTED();
 }
 
+NSDate* BluetoothLowEnergyDeviceMac::GetLastUpdateTime() const {
+  return last_update_time_.get();
+}
+
 std::string BluetoothLowEnergyDeviceMac::GetDeviceName() const {
   return base::SysNSStringToUTF8([peripheral_ name]);
 }