[Android] Add test cases for shouldOverrideUrlLoading.

This patch is to add test cases for shouldOverrideUrlLoading.
Most of the test cases are ported from android_webview, since the
implementation of some functions was different, so some test cases
were modified according to xwalk's implementation.
Why it's 0 for the load in `testNotCalledOnLoadUrl`, here it's 2 for above two `loadUrlSync`?