commit 5d7d30d174b0df5056e01ec3c7c07008f5ca1974
author szager <szager@chromium.org> Mon Apr 18 18:41:20 2016
committer Commit bot <commit-bot@chromium.org> Mon Apr 18 18:43:20 2016
tree 0536bb1b9dd567b2b844409ff0250b7f32b8f625
parent 1bc15aa1a2471e07a5ea74080fd871ee9926d339

IntersectionObserver: notify when root or target is removed.

If root and target were previously intersecting, and then DOM is
modified to remove root or target, or to make target not a
containing block descendant of root, send a notification.

Merge to M51; original patch:

https://codereview.chromium.org/1889053002

BUG=540528
TBR=ojan@chromium.org
NOTRY=true
NOPRESUBMIT=true

Review URL: https://codereview.chromium.org/1893423003

Cr-Commit-Position: refs/branch-heads/2704@{#100}
Cr-Branched-From: 6e53600def8f60d8c632fadc70d7c1939ccea347-refs/heads/master@{#386251}