Web Inspector: inspector/page/setShowPaintRects.html is a flakey failure since introduction

[patrickangle]

07992b5

Web Inspector: inspector/page/setShowPaintRects.html is a flakey failure since introduction
https://bugs.webkit.org/show_bug.cgi?id=233047
rdar://85345706

Reviewed by Antoine Quint.

Adding test results to the page causes a paint to be scheduled, which can cause paint rects to be requested at times we
are not expecting them as part of the flow of the test. We expect only our explicit change to an element to cause paints
to occur, but currently those paints end up interleaved with paints for adding results to the test page.

To resolve this, we now defer writing results to the test page until the end of each test case. This allows us to wait
to start each test case until there are no paint rects, and to avoid accidently causing a paint rect to appear at
inopportune times for our testing.

* LayoutTests/inspector/page/setShowPaintRects-expected.txt:
* LayoutTests/inspector/page/setShowPaintRects.html:
* LayoutTests/platform/mac/TestExpectations:

Canonical link: https://commits.webkit.org/251585@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@295580 268f45cc-cd09-0410-ab3c-d52691b4dbfc

[graouts]

Nice catch!

[webkit-early-warning-system]

Committed r295580 (251585@main): https://commits.webkit.org/251585@main

Reviewed commits have been landed. Closing PR #1541 and removing active labels.