Allow ddljson response to not contain an image

Interactive doodles don't use the image (data_uri field) included
in the ddljson response. Don't require that responses (on Desktop)
contain an image. Allow logo_cache to cache a doodle that doesn't
include an image.

Bug: 800170
Change-Id: I637ab2130db29efadecebd787c244e59008d3e63
Commit-Queue: Kyle Milka <>
Reviewed-by: Marc Treib <>
Cr-Commit-Position: refs/heads/master@{#623783}
9 files changed