Bug 968709 - Add a marionette test case to Bluetooth set to make sure the URL of Marionette client is correct. r=echou, f=vyang

Few marionette tests in unit-test set may navigate to specific URL and
wouldn't restore the URL of marionette client when the tests end.
Navigate the URL to default value before running Bluetooth test to make
sure the correctness of test.

dom/bluetooth/tests/marionette/manifest.ini

@@ -3,6 +3,7 @@ b2g = true
 browser = false
 qemu = true
 
+[test_navigate_to_default_url.py]
 [test_dom_BluetoothManager_enabled.js]
 [test_dom_BluetoothManager_adapteradded.js]
 [test_dom_BluetoothAdapter_setters.js]

dom/bluetooth/tests/marionette/test_navigate_to_default_url.py

@@ -0,0 +1,12 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from marionette_test import MarionetteTestCase
+
+class testNavigateToDefault(MarionetteTestCase):
+    def test_navigate_to_default_url(self):
+        try:
+            self.marionette.navigate("app://system.gaiamobile.org/index.html")
+        except:
+            self.assertTrue(Flase, "Can not navigate to system app.")