https://bugs.webkit.org/show_bug.cgi?id=38829

Reviewed by James Robinson.

Make compositing and CSS visibility play nicely together.

The main issue was that an old optimization (see bug 4377) caused
visibility:hidden layers to not appear in the z-order lists, but those
layers could still become composited, but would remain detached. In addition,
composited layers which were visibility:hidden would become visible sometimes.

With this fix, the z-order lists always contain all layers when the page
is in compositing mode. GraphicsLayer is changed to ensure that visibility:hidden
layers show no content, and visible descendants of hidden layers work correctly.

Tests: compositing/visibility/visibility-composited-transforms.html
       compositing/visibility/visibility-composited.html
       compositing/visibility/visibility-image-layers-dynamic.html
       compositing/visibility/visibility-image-layers.html

* platform/graphics/GraphicsLayer.cpp:
(WebCore::GraphicsLayer::GraphicsLayer): Init m_contentsVisible to true.
(WebCore::GraphicsLayer::dumpProperties): Dump m_contentsVisible if not true.
* platform/graphics/GraphicsLayer.h:
(WebCore::GraphicsLayer::contentsAreVisible): Getter for m_contentsVisible.
(WebCore::GraphicsLayer::setContentsVisible): Setter for m_contentsVisible.
* platform/graphics/ca/GraphicsLayerCA.cpp:
(WebCore::GraphicsLayerCA::setContentsVisible): Override setContentsVisible.
(WebCore::GraphicsLayerCA::commitLayerChangesBeforeSublayers): Handle ContentsVisibilityChanged
flag
(WebCore::GraphicsLayerCA::updateSublayerList): Only parent the m_contentsLayer if the layer
has visible contents.
(WebCore::GraphicsLayerCA::updateContentsVisibility): For bits painted into the layer itself,
we hide it by clearing the backing store.
* platform/graphics/ca/GraphicsLayerCA.h: Removed obsolete comment on the DrawsContentChanged flag,
added ContentsVisibilityChanged flag.
* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::updateZOrderLists): If we're in compositing mode, include all layers
in the z-order lists.
(WebCore::RenderLayer::collectLayers): New param to specify whether we need to collect all layers.
* rendering/RenderLayer.h:
(WebCore::RenderLayer::hasVisibleDescendant): Add comment about the need for an assertion in hasVisibleContent()
, and assertion in hasVisibleDescendant().
* rendering/RenderLayerBacking.cpp:
(WebCore::RenderLayerBacking::updateGraphicsLayerGeometry): Call setContentsVisible() on the GraphicsLayer.
(WebCore::RenderLayerBacking::isSimpleContainerCompositingLayer): We can use simple container layers in cases
where visibility:hidden causes layer content to not be drawn.
(WebCore::RenderLayerBacking::hasVisibleNonCompositingDescendants): Renamed from hasNonCompositingDescendants()
because it now also looks at visibility to decide when things are visible.
* rendering/RenderLayerBacking.h: hasNonCompositingDescendants() renamed to hasVisibleNonCompositingDescendants().

LayoutTests: The HTML5 video element in Safari does not respect "visibility:hidden" CSS property
https://bugs.webkit.org/show_bug.cgi?id=38829

Test various configurations of compositing layers and visibility.

Reviewed by James Robinson.

* compositing/visibility/visibility-composited-expected.png: Added.
* compositing/visibility/visibility-composited-transforms-expected.png: Added.
* compositing/visibility/visibility-composited-transforms.html: Added.
* compositing/visibility/visibility-composited.html: Added.
* compositing/visibility/visibility-image-layers-dynamic-expected.txt: Added.
* compositing/visibility/visibility-image-layers-dynamic.html: Added.
* compositing/visibility/visibility-image-layers-expected.png: Added.
* compositing/visibility/visibility-image-layers.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@98735 268f45cc-cd09-0410-ab3c-d52691b4dbfc