[wrt] Update the manifest file to Crosswalk 8

- Follow the bug xwalk-2136

Impacted TCs num(approved): New 0, Update 29, Delete 0
Unit test Platform: Android
Android test result summary: Pass 28, Fail 1, Block 0
Merge pull request #739 from wanghongjuan/wanghongjuan/wrt/security

[wrt] Update the manifest file to Crosswalk 8