Fix getting notified twice after subscribe to notifications and call readValue

device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm

Index: device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm
diff --git a/device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm b/device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm
index ae72118130f9cf810262344aa18969c4421c809d..2e2da4e618c0214d4907811847147a72b587390d 100644
--- a/device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm
+++ b/device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm
@@ -257,10 +257,12 @@ void BluetoothRemoteGattCharacteristicMac::DidUpdateValue(NSError* error) {
       callbacks.second.Run(error_code);
       return;
     }
-    UpdateValueAndNotify();
+    UpdateValue();
     callbacks.first.Run(value_);
   } else if (IsNotifying()) {
-    UpdateValueAndNotify();
+    UpdateValue();
+    gatt_service_->GetMacAdapter()->NotifyGattCharacteristicValueChanged(
+        this, value_);
   } else {
     // In case of buggy device, nothing should be done if receiving extra
     // read confirmation.
@@ -269,12 +271,10 @@ void BluetoothRemoteGattCharacteristicMac::DidUpdateValue(NSError* error) {
   }
 }
 
-void BluetoothRemoteGattCharacteristicMac::UpdateValueAndNotify() {
+void BluetoothRemoteGattCharacteristicMac::UpdateValue() {
   NSData* nsdata_value = cb_characteristic_.get().value;
   const uint8_t* buffer = static_cast<const uint8_t*>(nsdata_value.bytes);
   value_.assign(buffer, buffer + nsdata_value.length);
-  gatt_service_->GetMacAdapter()->NotifyGattCharacteristicValueChanged(this,
-                                                                       value_);
 }
 
 void BluetoothRemoteGattCharacteristicMac::DidWriteValue(NSError* error) {