With composited scrolling, content should only appear behind overlay scrollbars

We just need to update the clip of the scrolling layer to exclude the scrollbars when they're not overlay scrollbars.

Created attachment 175830 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 175830 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=175830&action=review

> Source/WebCore/ChangeLog:3
> +        With composited scrolling, content should only appear behind overlay scrollbars

This title is ambiguous. I think you mean "content should appear behind overlay scrollbars".

> Source/WebCore/rendering/RenderLayerBacking.cpp:744
> +        FloatSize clipSize = paddingBox.size();
> +        if (m_layerForHorizontalScrollbar && !m_owningLayer->horizontalScrollbar()->isOverlayScrollbar())
> +            clipSize.setHeight(clipSize.height() - m_layerForHorizontalScrollbar->size().height());
> +        if (m_layerForVerticalScrollbar && !m_owningLayer->verticalScrollbar()->isOverlayScrollbar())
> +            clipSize.setWidth(clipSize.width() - m_layerForVerticalScrollbar->size().width());

I think we have a "width for scrollbar" method somewhere that takes into account whether they are overlay scrollbars.

[Build Bot]

Comment on attachment 175830 [details]
Patch

Attachment 175830 [details] did not pass mac-ews (mac):
Output: http://queues.webkit.org/results/14975397

New failing tests:
compositing/overflow/clip-composited-content-under-overflow-controls.html

[WebKit Review Bot]

Comment on attachment 175830 [details]
Patch

Attachment 175830 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/14937845

New failing tests:
platform/chromium/virtual/softwarecompositing/overflow/clip-composited-content-under-overflow-controls.html
compositing/overflow/clip-composited-content-under-overflow-controls.html