[MSE] http/tests/media/media-source/mediasource-config-change-mp4-v-bitrate.html failing after r173318
https://bugs.webkit.org/show_bug.cgi?id=136676

Reviewed by Eric Carlson.

Source/WebCore:

Revert the inadvertant conditional change introduced in r173318.

* Modules/mediasource/MediaSource.cpp:
(WebCore::MediaSource::setDurationInternal):

LayoutTests:

* platform/mac/TestExpectations:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@173454 268f45cc-cd09-0410-ab3c-d52691b4dbfc