[usecase][xwalk-1326] Backup usecase of CSS Style Attribute

- This test case will be removed from demo-express(https://github.com/crosswalk-project/demo-express/pull/30), backup it as 'designed' in usecase
Merge pull request #1323 from haoxli/usecase/xwalk-1326

[usecase][xwalk-1326] Backup usecase of CSS Style Attribute