Pausable Object Cleanup - IntersectionObserverController

IntersectionObserver is using kInternalIntersectionObserver which
is a pausable task queue.

BUG=907125

Change-Id: I63fd26c407f32e64996f8e8a9af4ee860fc4daf6
Reviewed-on: https://chromium-review.googlesource.com/c/1388297
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622035}
5 files changed