Implement MediaStreamEvent constructor
https://bugs.webkit.org/show_bug.cgi?id=107411

Reviewed by Hajime Morita.

Fixed wrong test cases.

* fast/events/constructors/media-stream-event-constructor-expected.txt:
* fast/events/constructors/media-stream-event-constructor.html:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140315 268f45cc-cd09-0410-ab3c-d52691b4dbfc