The current documentation guidelines:
https://chromium.googlesource.com/chromium/src/+/HEAD/docs/README.md

Do not make any mention of how to add images to docs. This has caused many doc writers to add images as binary files to git:
https://cs.chromium.org/chromium/src/docs/images/

git does not handle large binary files well. It would be much better to have an out-of-band solution for images [gcl?]. This will likely require modification to gitiles as well to support this out-of-band solution.