render_pictures: adjust unittests to show specific failures

BUG=skia:2043,skia:2044
R=rmistry@google.com

Author: epoger@google.com

Review URL: https://codereview.chromium.org/139383004

git-svn-id: http://skia.googlecode.com/svn/trunk@13100 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed