[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.
Merge pull request #2287 from wuhengzhi/shouldOverrideUrlLoading_test

[Android] Add test cases for shouldOverrideUrlLoading.