Bluetooth: macOS: Implement BluetoothRemoteGattCharacteristicMac::UnsubscribeFromNotifications

device/bluetooth/test/mock_bluetooth_cbcharacteristic_mac.mm

Index: device/bluetooth/test/mock_bluetooth_cbcharacteristic_mac.mm
diff --git a/device/bluetooth/test/mock_bluetooth_cbcharacteristic_mac.mm b/device/bluetooth/test/mock_bluetooth_cbcharacteristic_mac.mm
index 31816c79a50847c2823cdb052bcec3dafd48e39f..2cc9eb7be148850b3e66989560e7438f8e7aa607 100644
--- a/device/bluetooth/test/mock_bluetooth_cbcharacteristic_mac.mm
+++ b/device/bluetooth/test/mock_bluetooth_cbcharacteristic_mac.mm
@@ -158,6 +158,23 @@ CBCharacteristicProperties GattCharacteristicPropertyToCBCharacteristicProperty(
 }
 
 - (void)simulateGattNotifySessionFailedWithError:(NSError*)error {
+  _notifying = NO;
+  CBPeripheral* peripheral = _service.peripheral;
+  [peripheral.delegate peripheral:peripheral
+      didUpdateNotificationStateForCharacteristic:self.characteristic
+                                            error:error];
+}
+
+- (void)simulateGattNotifySessionStopped {
+  _notifying = NO;
+  CBPeripheral* peripheral = _service.peripheral;
+  [peripheral.delegate peripheral:peripheral
+      didUpdateNotificationStateForCharacteristic:self.characteristic
+                                            error:nil];
+}
+
+- (void)simulateGattNotifySessionStoppedWithError:(NSError*)error {
+  _notifying = NO;
   CBPeripheral* peripheral = _service.peripheral;
   [peripheral.delegate peripheral:peripheral
       didUpdateNotificationStateForCharacteristic:self.characteristic