WebKit needs public performance tests running on public bots

WebKit needs public performance tests running on public bots
https://bugs.webkit.org/show_bug.cgi?id=10266

Reviewed by Adam Barth.

Completes the initial implementation of WebKit Perf bots. Add a build step for run-perf-test
and make google-mac-4 run it, and upload the results to webkit-perf.webkit.org.

* BuildSlaveSupport/build.webkit.org-config/config.json:
* BuildSlaveSupport/build.webkit.org-config/master.cfg:
(RunAndUploadPerfTests):
(RunAndUploadPerfTests.start):
(UploadPerfTestResults):
(BuildAndPerfTestFactory):
(BuildAndPerfTestFactory.__init__):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105848 268f45cc-cd09-0410-ab3c-d52691b4dbfc