rebaseline.py: fix --add-new when there are no expectations at all
BUG=skia:1582
R=rmistry@google.com

Review URL: https://codereview.chromium.org/23899003

git-svn-id: http://skia.googlecode.com/svn/trunk@11063 2bbb7eff-a529-9590-31e7-b0007b416f81
11 files changed