https://bugs.webkit.org/show_bug.cgi?id=145467
rdar://problem/18327239

Reviewed by Simon Fraser.

This patch ensures that overlap testing for composited layers works properly when the sibling
layer gets composited through its child.

When a layer gets composited through its child content, the recursive overlap testing should build up the
overlapmap stack so that sibling content is intersected both against the child and its parent bounds.

Source/WebCore:

Tests: compositing/sibling-layer-does-not-get-composited-overflow-hidden-case.html
       compositing/sibling-layer-does-not-get-composited-transform-case.html

* rendering/RenderLayerCompositor.cpp:
(WebCore::RenderLayerCompositor::addToOverlapMapRecursive):
(WebCore::RenderLayerCompositor::OverlapMap::contains): Deleted.

LayoutTests:

* compositing/sibling-layer-does-not-get-composited-overflow-hidden-case-expected.html: Added.
* compositing/sibling-layer-does-not-get-composited-overflow-hidden-case.html: Added.
* compositing/sibling-layer-does-not-get-composited-transform-case-expected.html: Added.
* compositing/sibling-layer-does-not-get-composited-transform-case.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@185019 268f45cc-cd09-0410-ab3c-d52691b4dbfc