[misc][XWALK-3000] Add usecase for File API PERSISTENT

Impacted tests(approved): new 1, update 0, delete 0
Unit test platform: [IVI]
Unit test result summary: pass 1, fail 0, block 0
Run the test needs a web server, the tinyweb is a web server in testkit-lite; For how to set, I will add a README file for this.