[GTK][AC] Clean up code related with the children management stuff for clutter based AC
https://bugs.webkit.org/show_bug.cgi?id=114260

Patch by ChangSeok Oh <changseok.oh@collabora.com> on 2013-04-29
Reviewed by Gustavo Noronha Silva.

Remove unused or usless code for children management stuff.

No new tests since no functionality changed.

* platform/graphics/clutter/GraphicsLayerActor.cpp:
(_GraphicsLayerActorPrivate):
(graphics_layer_actor_class_init):
(graphicsLayerActorAllocate):
(graphicsLayerActorDraw):
(graphicsLayerActorNew):
(graphicsLayerActorSetSublayers):
* platform/graphics/clutter/GraphicsLayerActor.h:
* platform/graphics/clutter/GraphicsLayerClutter.cpp:
(WebCore::idleDestroy):
(WebCore::GraphicsLayerClutter::ensureStructuralLayer):
(WebCore::GraphicsLayerClutter::updateLayerDrawsContent):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149281 268f45cc-cd09-0410-ab3c-d52691b4dbfc