RESOLVED INVALID 190105
Setting a style height value to the existing value still triggers a clone of StyleBoxData and thus slows down RenderStyle::diff 
https://bugs.webkit.org/show_bug.cgi?id=190105
Summary Setting a style height value to the existing value still triggers a clone of ...
Simon Fraser (smfr)
Reported 2018-09-28 20:36:19 PDT
If script keeps setting style.height to the same value, RenderStyle::setHeight still triggers access() which clones StyleBoxData, thus making future calls to RenderStyle::diff slower, since the pointer comparison fails. Probably true of most of the DataRef<> types.
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Simon Fraser (smfr)
Comment 1 2018-09-29 11:54:49 PDT
Seen in MotionMark leaves test.
Simon Fraser (smfr)
Comment 2 2018-09-29 16:05:06 PDT
Actually SET_VAR() already does a compareEqual(), so we're good.
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