rebaseline.py: improve readability of dry-run output

Split off of already-reviewed https://codereview.chromium.org/15789010/ ('rebaseline.py: --tests and --configs are now FILTERS within json results')

Review URL: https://codereview.chromium.org/16509006

git-svn-id: http://skia.googlecode.com/svn/trunk@9507 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed