[webkit-reviews] review requested: [Bug 94743] Automatically use composited scrolling : [Attachment 179166] Patch

[bugzilla-daemon at webkit.org]

vollick at chromium.org has asked	for review:
Bug 94743: Automatically use composited scrolling
https://bugs.webkit.org/show_bug.cgi?id=94743

Attachment 179166: Patch
https://bugs.webkit.org/attachment.cgi?id=179166&action=review

------- Additional Comments from vollick at chromium.org
Here is some performance data I gathered on the latest patch. My methodology
was
to do a trace while loading each of the pages (I stopped the verge once the
page
appeared; I didn't wait for it to pull the ads). I measured what I thought
could
be pain points affected by my patch.

With opting in enabled:
    gmail load:
      RenderLayerCompositor::updateCompositingLayers 180.446 ms
      RenderLayer::updateOutOfFlowPositioned 2.279 ms
      RenderLayer::updateDescendantDependentFlags 36.762 ms
      RenderLayer::updateNeedsCompositedScrolling 1.954 ms
      RenderLayerBacking::positionOverflowControlsLayers 0.079 ms
      RenderLayer::dirtyAncestorChainHasOutOfFlowPositionedDescendantStatus
8.064 ms
      RenderLayer::setAncestorChainHasOutOfFlowPositionedDescendant 0.109 ms

   the verge:
      RenderLayerCompositor::updateCompositingLayers 142.694 ms
      RenderLayer::updateOutOfFlowPositioned 3.314 ms
      RenderLayer::updateDescendantDependentFlags 42.278 ms
      RenderLayer::updateNeedsCompositedScrolling 1.979 ms
      RenderLayer::dirtyAncestorChainHasOutOfFlowPositionedDescendantStatus
0.397 ms
      RenderLayer::setAncestorChainHasOutOfFlowPositionedDescendant 0.424 ms

With opting in disabled:
    gmail load:
      RenderLayerCompositor::updateCompositingLayers 57.273 ms
      RenderLayer::updateOutOfFlowPositioned 2.408 ms
      RenderLayer::updateDescendantDependentFlags 64.563 ms
      RenderLayer::updateNeedsCompositedScrolling 1.402 ms
      RenderLayer::dirtyAncestorChainHasOutOfFlowPositionedDescendantStatus
8.091 ms
      RenderLayer::setAncestorChainHasOutOfFlowPositionedDescendant 0.097 ms

   the verge:
      RenderLayerCompositor::updateCompositingLayers 99.741 ms
      RenderLayer::updateOutOfFlowPositioned 2.87 ms
      RenderLayer::updateDescendantDependentFlags 23.787 ms
      RenderLayer::updateNeedsCompositedScrolling 1.473 ms
      RenderLayer::dirtyAncestorChainHasOutOfFlowPositionedDescendantStatus
0.856 ms
      RenderLayer::setAncestorChainHasOutOfFlowPositionedDescendant 0.47 ms