bluetooth: mac: Improve classic device discovery and update

device/bluetooth/bluetooth_classic_device_mac.mm

Index: device/bluetooth/bluetooth_classic_device_mac.mm
diff --git a/device/bluetooth/bluetooth_classic_device_mac.mm b/device/bluetooth/bluetooth_classic_device_mac.mm
index cc2fafb6e2632aa9bb6e1fdce078457a7a287035..da2866715b52fe55b41ae34780f775e0354a6daa 100644
--- a/device/bluetooth/bluetooth_classic_device_mac.mm
+++ b/device/bluetooth/bluetooth_classic_device_mac.mm
@@ -62,7 +62,9 @@ BluetoothUUID ExtractUuid(IOBluetoothSDPDataElement* service_class_data) {
 BluetoothClassicDeviceMac::BluetoothClassicDeviceMac(
     BluetoothAdapterMac* adapter,
     IOBluetoothDevice* device)
-    : BluetoothDeviceMac(adapter), device_([device retain]) {}
+    : BluetoothDeviceMac(adapter), device_([device retain]) {
+  UpdateTimestamp();
+}
 
 BluetoothClassicDeviceMac::~BluetoothClassicDeviceMac() {
 }
@@ -255,8 +257,9 @@ void BluetoothClassicDeviceMac::CreateGattConnection(
 }
 
 base::Time BluetoothClassicDeviceMac::GetLastUpdateTime() const {
-  return base::Time::FromDoubleT(
-      [[device_ getLastInquiryUpdate] timeIntervalSince1970]);
+  // getLastInquiryUpdate returns nil unpredictably so just use the
+  // cross platform implementation of last update time.
+  return last_update_time_;
 }
 
 int BluetoothClassicDeviceMac::GetHostTransmitPower(