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Without a background color, the page is transparent, which can make it
hard to read or notice whether it worked when the background behind it
is black. Also, add a console log to allow testing of setting the
console log level and DevTools.

Change-Id: Ib8c4197615b425addc8d44ef9e8e9275a97d4810
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2533862
Auto-Submit: David Dorwin <ddorwin@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826856}