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Just moved all the methods across for now to ensure tests were not
affected by this cleanup change. Some duplication (now within TABM)
could be cleaned up in future.

In prep for making an ABM factory as suggested by bsep@ in
crrev.com/c/2075001

Change-Id: Idcaad639bcc270a7ed3cc1f77f88b0fd5f2366a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2082220
Commit-Queue: Glen Robertson <glenrob@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746196}