MediaStream constructor test should cover ended MediaStreamTrack.
https://bugs.webkit.org/show_bug.cgi?id=110941

Reviewed by Kentaro Hara.

Spec: http://dev.w3.org/2011/webrtc/editor/getusermedia.html#mediastream
If tracks has ended, it should skip these tracks and continue with the next one.

* fast/mediastream/MediaStreamConstructor-expected.txt:
* fast/mediastream/MediaStreamConstructor.html:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144166 268f45cc-cd09-0410-ab3c-d52691b4dbfc