[Tizen] XWALK-951: Fail to launch crosswalk native UI on IVI

This bugs is caused by the following commit:
https://github.com/crosswalk-project/crosswalk/commit/2d7abedc56415276da93c34cc0c7ee552597d992

We still need to run crosswalk with url as a browser for testing, so
the change in runtime/browser/xwalk_browser_main_parts.cc needs to be
reverted.

https://crosswalk-project.org/jira/browse/XWALK-951