[GTK][AC] Adding contentsLayer for image and video
https://bugs.webkit.org/show_bug.cgi?id=113912

Reviewed by Gustavo Noronha Silva.

contentsLayer is a ClutterActor, which is added to the main layer
as a child when GraphicsLayer needs to render an image or video.

No new tests, already covered by existing AC tests.

* platform/graphics/clutter/GraphicsLayerActor.cpp:
(graphicsLayerActorUpdateTexture):
* platform/graphics/clutter/GraphicsLayerClutter.cpp:
(WebCore::GraphicsLayerClutter::GraphicsLayerClutter):
(WebCore::GraphicsLayerClutter::~GraphicsLayerClutter):
(WebCore):
(WebCore::GraphicsLayerClutter::setContentsToImage): Pass a Cairo surface to GraphicsLayer.
(WebCore::GraphicsLayerClutter::setContentsNeedsDisplay):
(WebCore::GraphicsLayerClutter::setContentsRect):
(WebCore::GraphicsLayerClutter::commitLayerChangesBeforeSublayers):
(WebCore::GraphicsLayerClutter::setupContentsLayer):
(WebCore::GraphicsLayerClutter::updateContentsImage): Set the Cairo surface for contentsLayer
to upload it as a texture.
(WebCore::GraphicsLayerClutter::updateContentsNeedsDisplay):
(WebCore::GraphicsLayerClutter::updateContentsRect):
(WebCore::GraphicsLayerClutter::updateSublayerList):
* platform/graphics/clutter/GraphicsLayerClutter.h:
(WebCore::GraphicsLayerClutter::hasContentsLayer):
(GraphicsLayerClutter):
(WebCore::GraphicsLayerClutter::contentsLayer):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148069 268f45cc-cd09-0410-ab3c-d52691b4dbfc