The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f739a39b76d1f0eb62579f27be422d4340ea8a84

commit f739a39b76d1f0eb62579f27be422d4340ea8a84
Author: Ian Kilpatrick <ikilpatrick@chromium.org>
Date: Fri Mar 16 20:39:16 2018

[shapes] Remove shape-outside avoiding behaviour for new-FCs/replaced.

See intent: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/pfDg-VAeKWs

This makes new formatting contexts behave exactly like floats would
when they are positioned. I.e. they don't look at the shape-outside
of the float, and instead as positioned for their margin box.

I've added a .tentative test as per the intent.

This will allow us to have a (relatively) simple implementation of
css-shapes in LayoutNG as we only have to consider the shape area for
line-boxes. \o/

Bug:  820520 
Change-Id: Ib07600a291eb4838675a9a1068c5fc16cac0633f
Reviewed-on: https://chromium-review.googlesource.com/739961
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543813}
[add] https://crrev.com/f739a39b76d1f0eb62579f27be422d4340ea8a84/third_party/WebKit/LayoutTests/external/wpt/css/css-shapes/shape-outside/formatting-context/reference/shape-outside-formatting-context-ref.html
[add] https://crrev.com/f739a39b76d1f0eb62579f27be422d4340ea8a84/third_party/WebKit/LayoutTests/external/wpt/css/css-shapes/shape-outside/formatting-context/shape-outside-formatting-context.tentative.html
[modify] https://crrev.com/f739a39b76d1f0eb62579f27be422d4340ea8a84/third_party/WebKit/Source/core/layout/FloatingObjects.h
[modify] https://crrev.com/f739a39b76d1f0eb62579f27be422d4340ea8a84/third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp
[modify] https://crrev.com/f739a39b76d1f0eb62579f27be422d4340ea8a84/third_party/WebKit/Source/core/layout/LayoutBlockFlow.h
[modify] https://crrev.com/f739a39b76d1f0eb62579f27be422d4340ea8a84/third_party/WebKit/Source/core/layout/LayoutBox.cpp