[AdTagging] Remove .Google. ad histograms

What:
Remove the .Google. Ads histograms, leaving only .SubresourceFilter.
John will rename those in an upcoming CL.

Why:
We're focusing on the ads detected by AdTagging at this point and no
longer need the Google histograms.

How:
Most of the changes for this are in tests. The browser tests used to
use the iframe's name as a means of ad detection for cases where the
iframe doesn't have a url (e.g., doc.written frames). Now, doc.written
ad iframes are detected because they're created by known ad scripts.

Bug: 884233
Change-Id: I08cbecc9f70f698d24529e50aa1cde8db1de0981
Reviewed-on: https://chromium-review.googlesource.com/c/1403092
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Commit-Queue: Josh Karlin <jkarlin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621755}
12 files changed