[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.
For the data load, shouldOverrideUrlLoading was not called, testNotCalledOnLoadUrl should be changed to testNotCalledOnLoadData, it's more reasonable. thanks.