rebaseline.py: use specified configs/tests as a FILTER over actually-run tests

Now that we have the actual-results.json file for every bot type, we know
the full set of tests that actual results are available for. If configs and/or
tests are specified, just use those as FILTERS over the actually available
results.

R=senorblanco@chromium.org

Review URL: https://codereview.chromium.org/18324018

git-svn-id: http://skia.googlecode.com/svn/trunk@9956 2bbb7eff-a529-9590-31e7-b0007b416f81
8 files changed