The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/54e2583f13883cfdb1cff8d08f4a031d8af65d83

commit 54e2583f13883cfdb1cff8d08f4a031d8af65d83
Author: Stefan Zager <szager@chromium.org>
Date: Tue Aug 14 22:15:31 2018

[IntersectionObserverV2] OOPIF support

This patch adds a flag indicating whether an iframe element is occluded
or has visual effects applied in the parent document; and adds the flag
to the IPC message containing the iframe's intersection with the
parent's viewport.

BUG= 869049 
R=kenrb@chromium.org,chrishtr@chromium.org

Change-Id: I0891a3e6740dbce39f0cf0120353feb8c9fca173
Reviewed-on: https://chromium-review.googlesource.com/1167960
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583055}
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/browser/frame_host/cross_process_frame_connector.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/browser/frame_host/cross_process_frame_connector.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/browser/renderer_host/frame_connector_delegate.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/browser/renderer_host/render_widget_host_view_child_frame.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/browser/renderer_host/render_widget_host_view_child_frame.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/browser/renderer_host/render_widget_host_view_child_frame_unittest.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/browser/site_per_process_browsertest.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/common/frame_messages.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/common/view_messages.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/renderer/render_frame_proxy.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/renderer/render_frame_proxy.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/renderer/render_widget.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/content/renderer/render_widget.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/WebKit/LayoutTests/TestExpectations
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/WebKit/LayoutTests/VirtualTestSuites
[add] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/WebKit/LayoutTests/http/tests/intersection-observer/resources/v2-subframe.html
[add] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/WebKit/LayoutTests/http/tests/intersection-observer/v2/cross-origin-effects.html
[add] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/WebKit/LayoutTests/http/tests/intersection-observer/v2/cross-origin-occlusion.html
[add] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/WebKit/LayoutTests/virtual/intersection-observer-v2/http/tests/intersection-observer/README.txt
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/public/web/web_frame_widget.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/public/web/web_remote_frame_client.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/local_frame.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/local_frame.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/remote_frame_client.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/remote_frame_client_impl.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/remote_frame_client_impl.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/remote_frame_view.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/remote_frame_view.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/web_frame_widget_impl.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/frame/web_frame_widget_impl.h
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/intersection_observer/intersection_observation.cc
[modify] https://crrev.com/54e2583f13883cfdb1cff8d08f4a031d8af65d83/third_party/blink/renderer/core/loader/empty_clients.h

Is there still work to be done on this? I thought the patch above was sufficient.

Fixed.