Improve webkit-patch rebaseline to work for more cases

Improve webkit-patch rebaseline to work for more cases
https://bugs.webkit.org/show_bug.cgi?id=90504

Reviewed by Dirk Pranke.

-Makes it work for the build.chromium.org bots.
-Lets you rebaseline all builders instead of just one.
-Lets you pass in the builder or test to rebaseline.

* Scripts/webkitpy/common/net/buildbot/buildbot.py:
(Build.results_url):
Make this work for build.chromium.org builders as well.

* Scripts/webkitpy/common/net/buildbot/chromiumbuildbot.py:
(ChromiumBuilder):
(ChromiumBuilder.latest_cached_build):
ChromiumBuilder doesn't support large parts of the Builder interface.
This provides the bare minimum for this patch to work. Eventually,
we should create a single interface that can be supported for both
sets of buildbots.

* Scripts/webkitpy/layout_tests/port/builders.py:
(builder_path_from_name):
(all_builder_names):
memoizing here is incorrect because the test override _exact_matches,
so these can return different values. In either case, I'm pretty sure these
are not remotely hot codepaths.

* Scripts/webkitpy/tool/commands/rebaseline.py:
(AbstractParallelRebaselineCommand.__init__):
(Rebaseline):
(Rebaseline.__init__):
(Rebaseline._builders_to_pull_from):
(Rebaseline._builder_with_name):
(Rebaseline._tests_to_update):
(Rebaseline.execute):
* Scripts/webkitpy/tool/commands/rebaseline_unittest.py:
(test_rebaseline.mock_builders_to_pull_from):
(test_rebaseline):
(test_rebaseline_command_line_flags):
(test_rebaseline_multiple_builders):
(test_rebaseline_multiple_builders.mock_builders_to_pull_from):
(test_rebaseline_multiple_builders.mock_tests_to_update):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121821 268f45cc-cd09-0410-ab3c-d52691b4dbfc