Revert "Allow ddljson response to not contain an image"

This reverts commit bf7b0cb7ff8897c1e1160c48dc2dcfca0c37329e.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> 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
> Reviewed-on: https://chromium-review.googlesource.com/c/1405431
> Commit-Queue: Kyle Milka <kmilka@chromium.org>
> Reviewed-by: Marc Treib <treib@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#623783}

TBR=treib@chromium.org,kmilka@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 800170
Change-Id: Ided4301b88586d21cbb653aefaf75206aa6d2c5d
Reviewed-on: https://chromium-review.googlesource.com/c/1426879
Reviewed-by: Kyle Milka <kmilka@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624813}
9 files changed