add --readJsonSummaryPath to render_pictures

BUG=skia:1942
R=borenet@google.com

Author: epoger@google.com

Review URL: https://codereview.chromium.org/273783004

git-svn-id: http://skia.googlecode.com/svn/trunk@14695 2bbb7eff-a529-9590-31e7-b0007b416f81
6 files changed