Bug 1693885 [wpt PR 27710] - [layout] Don't allow non-formatting-context to be relayout-roots., a=testonly

Automatic update from web-platform-tests [layout] Don't allow non-formatting-context to be relayout-roots. As lots of state can be passed from a non-fc to its sibling, treating these as formatting context roots is incorrect for lots of edge cases. This patch dis-allows non-fcs to be relayout-roots. Change-Id: Ieef1a2ad1d653bd954a8a9989aecc8ac83107f69 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2707136 Reviewed-by: Morten Stenshorne <mstensho@chromium.org> Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org> Cr-Commit-Position: refs/heads/master@{#856317} -- wpt-commits: dfe483887469f2ad966d6244910b7aa5f0cfbb7b wpt-pr: 27710
2021-02-22 22:07:15 +00:00 · 2021-02-22 22:07:15 +00:00 · b71193e801
--- a/testing/web-platform/tests/css/CSS2/normal-flow/margin-collapsing-dynamic.html
+++ b/testing/web-platform/tests/css/CSS2/normal-flow/margin-collapsing-dynamic.html
@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<link rel="match" href="../../reference/ref-filled-green-100px-square.xht" />
+<link rel="help" href="https://www.w3.org/TR/CSS22/box.html#collapsing-margins" title="8.3.1 Collapsing margins">
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+<div style="width: 100px; height: 100px; background: green;"></div>
+<div style="width: 0; height: 0; outline: solid red 50px; position: relative; z-index: 1; overflow: clip; margin-left: 50px;">
+  <div id="target"></div>
+</div>
+<script>
+document.body.offsetTop;
+document.getElementById('target').style.marginTop = '-1000px';
+</script>