REGRESSION (r266634): [macOS release] TestWebKitAPI.WebKit.WKThumbnailViewResetsViewStateWhenUnparented is a flaky failure

[Ryan Haddad]

The following API test recently became a flaky failure on macOS release bots:

    TestWebKitAPI.WebKit.WKThumbnailViewResetsViewStateWhenUnparented
        _RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
        
        /Volumes/Data/slave/mojave-release/build/Tools/TestWebKitAPI/Tests/WebKit/WKThumbnailView.mm:300
        Value of: [[webView objectByEvaluatingJavaScript:@"window.internals.isPageActive()"] boolValue]
          Actual: false
        Expected: true

https://results.webkit.org/?suite=api-tests&test=TestWebKitAPI.WebKit.WKThumbnailViewResetsViewStateWhenUnparented

[Radar WebKit Bug Importer]

<rdar://problem/68487302>

[Ryan Haddad]

Looks like it started at or around https://trac.webkit.org/changeset/266634/webkit

[Ryan Haddad]

(In reply to Ryan Haddad from comment #2)
> Looks like it started at or around
> https://trac.webkit.org/changeset/266634/webkit
Hm, this change may affecting some layout tests, too:
https://results.webkit.org/?suite=layout-tests&suite=layout-tests&suite=layout-tests&suite=layout-tests&test=compositing%2Ftiling%2Ftiled-mask-inwindow.html&test=fast%2Fevents%2Fpage-visibility-iframe-move-test.html&test=pageoverlay%2Foverlay-remove-reinsert-view.html&test=tiled-drawing%2Ftiled-backing-in-window.html

[Sihui Liu]

I already filed a bug about this and proposed a fix: https://bugs.webkit.org/show_bug.cgi?id=216258. 

About layout tests, I can only reproduce failure of fast/animation/request-animation-frame-throttling-lowPowerMode.html so far: https://bugs.webkit.org/show_bug.cgi?id=216261.

*** This bug has been marked as a duplicate of bug 216258 ***

[Ryan Haddad]

(In reply to Sihui Liu from comment #4)
> I already filed a bug about this and proposed a fix:
> https://bugs.webkit.org/show_bug.cgi?id=216258. 
> 
> About layout tests, I can only reproduce failure of
> fast/animation/request-animation-frame-throttling-lowPowerMode.html so far:
> https://bugs.webkit.org/show_bug.cgi?id=216261.
> 
> *** This bug has been marked as a duplicate of bug 216258 ***

I can reproduce at least one of the failures. Filed https://bugs.webkit.org/show_bug.cgi?id=216275.