GitLab

Deregistering the handlers avoids them being called once the packing
operation is done, and an unrelated future pack operation is in
progress. It also frees up a bit of memory.

BUG=791895

Change-Id: I52b8382d18b95637c868c1cdb91fed4b0f6fd276
Reviewed-on: https://chromium-review.googlesource.com/c/1317208Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Anand Mistry <amistry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605540}