Replace sleep with explicit wait and re-enable: video player test

gaiatest/tests/manifest.ini

@@ -58,6 +58,5 @@ carrier = true
 disabled = TODO
 [test_video_player.py]
 sdcard = true
-disabled = Often failing due to timing issues - github issue #165
 [test_launch_app.py]
 wifi = true

gaiatest/tests/test_video_player.py

@@ -48,16 +48,16 @@ def test_play_video(self):
         self.wait_for_element_displayed(*self._video_frame_locator)
         self.wait_for_element_displayed(*self._video_loaded_locator)
 
+        # Wait for vid to have started playing
+        self.assertTrue(self.marionette.execute_script("return window.wrappedJSObject.playing;"))
+
         # Tap to make toolbar visible
         self.marionette.tap(self.marionette.find_element(*self._video_frame_locator))
 
-        # Let video play for one second
-        time.sleep(1)
-
-        # The elapsed time > 0:00 is the only indication of the video playing
-        self.assertIsNotNone(self.marionette.find_element(*self._elapsed_text_locator).text)
+        # The elapsed time != 0:00 is the only indication of the toolbar visible
         self.assertNotEqual(self.marionette.find_element(*self._elapsed_text_locator).text, "00:00")
 
+        # Check the name too. This will only work if the toolbar is visible
         self.assertEqual(first_video_name,
                         self.marionette.find_element(*self._video_title_locator).text)