https://bugs.webkit.org/show_bug.cgi?id=96203

Reviewed by Dirk Pranke.

Often in debug builds, the first tests in each worker crash because they
can't yet open the Xvfb display assigned to them. This indicates Xvfb hasn't
yet been set up.

To avoid this, the execution should halt for a small amount of time before tests
are run so the Xvfb process has enough time to get ready. At the moment this is
done right after the Xvfb process is spawned and the execution halts for one
second. That value is overriden to zero when testing to not prolong the testing time.

* Scripts/webkitpy/layout_tests/port/xvfbdriver.py:
(XvfbDriver.__init__):
(XvfbDriver._start):
* Scripts/webkitpy/layout_tests/port/xvfbdriver_unittest.py:
(XvfbDriverTest.make_driver):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@130192 268f45cc-cd09-0410-ab3c-d52691b4dbfc