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The code for this was mostly already written, but its use was commented
out, so the callbacks weren't being run.

Also, we now use Bind{Once,Repeating} for these callbacks.

Bug: 892889
Change-Id: I544de97a511286236cc9c4ad7a89e094aed202f5
Reviewed-on: https://chromium-review.googlesource.com/c/1283729Reviewed-by: Paul Meyer <paulmeyer@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601289}