Revert of IntersectionObserver: use an idle callback to send notifications. (patchset #6 id:100001 of https://codereview.chromium.org/1776493002/ )

Reason for revert:
Tests added are leaking, https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Leak/builds/18011

Original issue's description:
> IntersectionObserver: use an idle callback to send notifications.
>
> With this change, the tests can no longer use setTimeout(0) to wait
> for notifications to be delivered.  Instead, use takeRecords() to
> proactively grab notifications right after they are generated
> (typically in a RAF right after a layout change).
>
> BUG=540528
> R=ojan@chromium.org,haraken@chromium.org
>
> Committed: https://crrev.com/2c168f38b5c0e4e50374be4e54c44901c60738a9
> Cr-Commit-Position: refs/heads/master@{#380278}

TBR=ojan@chromium.org,haraken@chromium.org,skyostil@chromium.org,szager@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=540528

Review URL: https://codereview.chromium.org/1780163002

Cr-Commit-Position: refs/heads/master@{#380375}
19 files changed