[GTK][AC] use a smart pointer for GList and ClutterCanvas
https://bugs.webkit.org/show_bug.cgi?id=114057

Patch by ChangSeok Oh <changseok.oh@collabora.com> on 2013-04-11
Reviewed by Gustavo Noronha Silva.

We can make simple code & prevent possible memory leak by using a proper smart pointer.
Especially if we get children by clutter_actor_get_children, we should free it after using.

No functionality changed.

* platform/graphics/clutter/GraphicsLayerActor.cpp:
(graphicsLayerActorUpdateTexture):
(graphicsLayerActorRemoveAll):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148202 268f45cc-cd09-0410-ab3c-d52691b4dbfc