[wrt][xwalk-2656] Update TCs and README file

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: Android
Android test result summary: Pass 1, Fail 0, Block 0
Merge pull request #1073 from wanghongjuan/wanghongjuan/wrt/xwalk-2656

[wrt][xwalk-2656] Update TCs and README file