Mark images for manual rebaseline for BUG=420479

This is a prerequisite for the landing of chromium patch
https://codereview.chromium.org/688483002

BUG=420749

NOTRY=true

Review URL: https://codereview.chromium.org/711573002

git-svn-id: svn://svn.chromium.org/blink/trunk@184933 bbb929c8-8fbe-4397-9dbb-9b2b20218538