[Bluetooth][WinRT] Perform Explicit Connection Check

This change contains a small fix to perform an explicit connection check
after receiving a BluetoothLEDevice instance. This is necessary for
paired devices, where the connection handler gets registered too late to
get notified of the initial GATT connection initiated by the OS.

Bug: 821766
Change-Id: Ic022035f101324daa9a0772940740550e948e5fb
Reviewed-on: https://chromium-review.googlesource.com/1154920Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579338}

device/bluetooth/bluetooth_device_winrt.cc

@@ -344,6 +344,13 @@ void BluetoothDeviceWinrt::OnFromBluetoothAddress(
       base::BindRepeating(&BluetoothDeviceWinrt::OnConnectionStatusChanged,
                           weak_ptr_factory_.GetWeakPtr()));
 
+  // For paired devices the OS immediately establishes a GATT connection after
+  // the first advertisement. In this case our handler is registered too late to
+  // catch the initial connection changed event, and we need to perform an
+  // explicit check ourselves.
+  if (IsGattConnected())
+    DidConnectGatt();
+
   if (gatt_services_changed_token_) {
     RemoveGattServicesChangedHandler(ble_device_.Get(),
                                      *gatt_services_changed_token_);