[webapi] Integrate 75 tests for FileWriterAPI

- approved: 18, designed: 57

Impacted tests(approved): new 18, update 0, delete 0
Unit test platform: [IVI] crosswalk-10.38.222, t-e-c 0.107
Unit test result summary: pass 18, fail 0, block 0
Merge pull request #1166 from xinliux/filewriterapi-integrate

[webapi] Integrate 75 tests for FileWriterAPI