add --writeChecksumBasedFilenames flag to render_pictures

BUG=skia:1455,skia:2230
R=robertphillips@google.com, robertphillips@chromium.org

Author: epoger@google.com

Review URL: https://codereview.chromium.org/202983003

git-svn-id: http://skia.googlecode.com/svn/trunk@13859 2bbb7eff-a529-9590-31e7-b0007b416f81
9 files changed