Fix issue with reflections and composited layers

Fix issue with reflections and composited layers
https://bugs.webkit.org/show_bug.cgi?id=82636

Source/WebCore:

Reviewed by Alexey Proskuryakov

When tearing down GraphicsLayers which referene eachother via m_replicatedLayer/m_replicaLayer,
we need to clean up the replica layer pointers.

No new tests; tested by existing compositing and repaint tests.

* platform/graphics/GraphicsLayer.cpp:
(WebCore::GraphicsLayer::~GraphicsLayer):
(WebCore::GraphicsLayer::setReplicatedByLayer):

LayoutTests:

Reviewed by Alexey Proskuryakov

Unskip some compositing tests that should pass now.

* platform/mac-wk2/Skipped:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@112939 268f45cc-cd09-0410-ab3c-d52691b4dbfc