[wrt][xwalk-2412] Update case description

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: Android
Android test result summary: Pass 1, Fail 0, Block 0
[wrt][xwalk-1507/1508/1509/1510] Move 4 TCs from tizen2.3/wrt

- Those TCs feature has not been resolved

Impacted TCs num(designed): New 4, Update 0, Delete 0
Merge pull request #808 from wanghongjuan/wanghongjuan/wrt/xwalk-2412

[wrt][xwalk-2412] Update case description
Merge pull request #809 from wanghongjuan/wanghongjuan/wrt/tizen-legacy

[wrt][xwalk-1507/1508/1509/1510] Move 4 TCs from tizen2.3/wrt