[CSS Blending] Blending doesn't work if the parent stacking context is not a self painting layer
https://bugs.webkit.org/show_bug.cgi?id=130891

Patch by Ion Rosca <rosca@adobe.com> on 2014-05-07
Reviewed by Dean Jackson.

Source/WebCore:
The stacking context layers having unisolated blending descendants should be able
to create transparency layers or to become composited in order to restrict blending
content to accessing the information outside the current stacking context.
Some layers are not self painting layers and these layers cannot crate transparency
layers and cannot be composited, thus they are not able to isolate blending descendants
when it's required.

The solution in this patch is to make a layer isSelfPaintingLayer when
it needs to isolate blending descendants (hasUnisolatedBlendingDescendants).

Tests: css3/blending/blend-mode-isolation-accelerated-overflow-hidden.html
       css3/blending/blend-mode-isolation-overflow-hidden.html
       css3/blending/blend-mode-isolation-turn-off-self-painting-layer.html
       css3/blending/blend-mode-isolation-turn-off-self-painting-layer1.html
       css3/blending/blend-mode-isolation-turn-off-self-painting-layer2.html
       css3/blending/blend-mode-isolation-turn-on-self-painting-layer.html

* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::updateAncestorChainHasBlendingDescendants):
When hasUnisolatedBlendingDescendants is set we make sure that isSelfPaintingLayer flag is set too.
(WebCore::RenderLayer::updateDescendantDependentFlags):
The flags might be read or changed while walking the descendants, so we don't want to reset
them before traversing the tree.
(WebCore::RenderLayer::shouldBeSelfPaintingLayer):
Adding isolatesBlending() condition for a layer to be self painting.
* rendering/RenderLayer.h:
Removing ASSERT from hasUnisolatedBlendingDescendants(). It crashes in minibrowser
and in layout tests when painting contents. Similar bugs on other flags: #71044, #71277.
* rendering/RenderLayerModelObject.cpp:
(WebCore::RenderLayerModelObject::styleDidChange):
Telling ancestors that blend mode property has been removed from CSS when the layer for
this element is going to be removed; styleChanged will not be called anymore.

LayoutTests:
Removed position:relative which forced tests to avoid this bug.
* css3/blending/blend-mode-accelerated-parent-overflow-hidden.html:
* css3/blending/blend-mode-clip-accelerated-blending-canvas.html:
* css3/blending/blend-mode-clip-accelerated-blending-child.html:
* css3/blending/blend-mode-clip-accelerated-blending-with-siblings.html:
* css3/blending/blend-mode-clip-accelerated-transformed-blending.html:

New tests:
* css3/blending/blend-mode-isolation-accelerated-overflow-hidden-expected.txt: Added.
* css3/blending/blend-mode-isolation-accelerated-overflow-hidden.html: Added.
* css3/blending/blend-mode-isolation-overflow-hidden-expected.html: Added.
* css3/blending/blend-mode-isolation-overflow-hidden.html: Added.
* css3/blending/blend-mode-isolation-turn-off-self-painting-layer-expected.txt: Added.
* css3/blending/blend-mode-isolation-turn-off-self-painting-layer.html: Added.
* css3/blending/blend-mode-isolation-turn-off-self-painting-layer1-expected.txt: Added.
* css3/blending/blend-mode-isolation-turn-off-self-painting-layer1.html: Added.
* css3/blending/blend-mode-isolation-turn-off-self-painting-layer2-expected.txt: Added.
* css3/blending/blend-mode-isolation-turn-off-self-painting-layer2.html: Added.
* css3/blending/blend-mode-isolation-turn-on-self-painting-layer-expected.txt: Added.
* css3/blending/blend-mode-isolation-turn-on-self-painting-layer.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@168462 268f45cc-cd09-0410-ab3c-d52691b4dbfc