[Texmap][GTK] The poster-circle doesn't appear.

https://bugs.webkit.org/show_bug.cgi?id=106672

Patch by ChangSeok Oh <shivamidow@gmail.com> on 2013-01-21
Reviewed by Noam Rosenthal.

Source/WebCore:

We need to call setNeedsDisplay to redraw GraphicsLayer after we set drawsContent
a new value for the layer. Otherwise we can't get a chance for first drawing the layer.

Test: compositing/visibility/visibility-composited-animation.html

* platform/graphics/texmap/TextureMapperLayer.cpp:
(WebCore::TextureMapperLayer::flushCompositingStateForThisLayerOnly):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140347 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Task-number: QTBUG-33081
Change-Id: Idf95bb5341cc4bc3fdf6d585b52c8b949e3ccb67
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>