If there is more then one agent accepts current pause, we should resume
only when last agent is disabled.

R=dgozman@chromium.org

Bug: chromium:834056
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I2904b3f4ab76117511e16450dd575ebf3e20a068
Reviewed-on: https://chromium-review.googlesource.com/1041207Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52931}