NEW 203112
A combination of scrolling and a content change can leave a fixed layer in the wrong place 
https://bugs.webkit.org/show_bug.cgi?id=203112
Summary A combination of scrolling and a content change can leave a fixed layer in th...
Simon Fraser (smfr)
Reported 2019-10-17 10:51:25 PDT
The patch in bug 196612 changes scrollingcoordinator/ios/ui-scroll-fixed.html to avoid this bug, but we should fix the underlying bug too. The bug is that a UI scroll can cause an offset to be applied to a CALayer in the UI process, but the combination of a content change and the scroll means that the GraphicsLayerCA ends up with the same position it had before. When that layer+scrolling tree is committed, nothing fixes up the CALayer position in the UI process. We can also leave a wrong "approximate position" on the GraphicsLayer in this situation.
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