Chromium DumpRenderTree dumps a core every time it's run (Linux/Debug)
https://bugs.webkit.org/show_bug.cgi?id=111440

Reviewed by Adrienne Walker.

Remove unnecessary WebCompositorSupport::shutdown call

* DumpRenderTree/chromium/DumpRenderTree.cpp:
(main):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144775 268f45cc-cd09-0410-ab3c-d52691b4dbfc