Unreviewed, rolling out r156725.

Unreviewed, rolling out r156725.
http://trac.webkit.org/changeset/156725
https://bugs.webkit.org/show_bug.cgi?id=122176

broke all the mismatch tests again (Requested by thorton on
#webkit).

Tools:

* WebKitTestRunner/mac/PlatformWebViewMac.mm:
(WTR::PlatformWebView::PlatformWebView):

LayoutTests:

* platform/mac-wk2/tiled-drawing/window-server-snapshots-work-expected-mismatch.html: Removed.
* platform/mac-wk2/tiled-drawing/window-server-snapshots-work.html: Removed.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@156731 268f45cc-cd09-0410-ab3c-d52691b4dbfc