[webapi] Integrate 161 tests for Web Audio

- Update window.AudioContext to new AudioContext()
- approved: 113, designed: 48

Impacted tests(approved): new 113, update 0, delete 0
Unit test platform: [IVI] crosswalk-10.38.222, t-e-c 0.107
Unit test result summary: pass 113, fail 0, block 0
Merge pull request #1171 from xinliux/webaudio-integrate

[webapi] Integrate 161 tests for Web Audio