[usecase-webapi][XWALK-2287] Fix bug for MediaQueries

- Update the description for the test

Impacted tests(approved): new 0, update 1, delete 0
Unit test platform: [Andriod]
Unit test result summary: pass 1, fail 0, block 0
Still not understand what do these mean. Do you mean the end user must know his device aspect ratio and the device height in pixel? This is not a reasonable requirement.

Another, for the ordered lists, why not use `<ol>`?