webkit-patch rebaseline-expectations should share code with rebaseline-all

webkit-patch rebaseline-expectations should share code with rebaseline-all
https://bugs.webkit.org/show_bug.cgi?id=90413

Reviewed by Dirk Pranke.

Make them share code. In addition to reducing code duplication this makes
rebaseline-expectations considerably faster by rebaselining in parallel.

* Scripts/webkitpy/tool/commands/rebaseline.py:
(AbstractParallelRebaselineCommand):
(AbstractParallelRebaselineCommand._run_webkit_patch):
(AbstractParallelRebaselineCommand._rebaseline):
(RebaselineJson):
(RebaselineJson.execute):
(RebaselineExpectations):
(RebaselineExpectations._update_expectations_file):
(RebaselineExpectations._tests_to_rebaseline):
(RebaselineExpectations._add_tests_to_rebaseline_for_port):
(RebaselineExpectations.execute):
* Scripts/webkitpy/tool/commands/rebaseline_unittest.py:
(test_rebaseline_all):
(test_rebaseline_expectations.run_in_parallel):
(test_rebaseline_expectations):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121724 268f45cc-cd09-0410-ab3c-d52691b4dbfc