https://bugs.webkit.org/show_bug.cgi?id=123537

Source/WebCore:

Reviewed by Tim Horton.

We call rendererBackgroundColor() to determine the layer's background color,
but on most elements this returns the transparent color (a valid color).
This caused us to allocate a contentsLayer, and use the transparent color as its
backgroundColor, which was wasteful.

Fix by only making a background-color layer if the color is not transparent (zero alpha).

Also avoid making a new contents layer on every color change, and make sure that
we don't do implicit animations for backgroundColor, and some other properties
that were omitted by mistake.

Layer tree dumps don't dump content layers, so no way to test easily.

* platform/graphics/ca/GraphicsLayerCA.cpp:
(WebCore::GraphicsLayerCA::setContentsToSolidColor):
* platform/graphics/ca/mac/PlatformCALayerMac.mm:
(nullActionsDictionary):

Source/WebKit2:

Reviewed by Tim Horton.

Add some properties to the list of things not to implicitly animate.

* Shared/mac/RemoteLayerTreePropertyApplier.mm:
(WebKit::RemoteLayerTreePropertyApplier::disableActionsForLayer):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158889 268f45cc-cd09-0410-ab3c-d52691b4dbfc