[webkit-reviews] review denied: [Bug 109302] Simplify logic for automatically opting into composited scrolling : [Attachment 188637] Patch

[bugzilla-daemon at webkit.org]

Simon Fraser (smfr) <simon.fraser at apple.com> has denied Glenn Hartmann
<hartmanng at chromium.org>'s request for review:
Bug 109302: Simplify logic for automatically opting into composited scrolling
https://bugs.webkit.org/show_bug.cgi?id=109302

Attachment 188637: Patch
https://bugs.webkit.org/attachment.cgi?id=188637&action=review

------- Additional Comments from Simon Fraser (smfr) <simon.fraser at apple.com>
View in context: https://bugs.webkit.org/attachment.cgi?id=188637&action=review


> Source/WebCore/rendering/RenderLayer.cpp:5298
> -    bool shouldUpdateDescendantsAreContiguousInStackingOrder =
isStackingContext() && (m_zOrderListsDirty || m_normalFlowListDirty);
> +    bool shouldUpdateCanBeStackingContainer = isStackingContext() &&
(m_zOrderListsDirty || m_normalFlowListDirty);

Only composited scrolling uses the stacking container logic. You need to avoid
all the work to update the flag when the layer is not a candidate for
composited scrolling, otherwise you'll slow everything down.