usecase-wrt][XWALK-1177]Add Web Dynamic Box tcs

Impacted TCs num(designed): New 1, update 0, deleted 0
Unit test platform: [tizen]
Merge pull request #1057 from linshen/shenlin/add-usecase-XWALK-1177

usecase-wrt][XWALK-1177]Add Web Dynamic Box tcs