Reviewed by Mark Rowe.

        Don't delete the decoder if it's already been created. The one we have
        is fine.

        Cairo image cleanups. Nothing substantial.

        Notify ImageObservers where appropriate.

        * platform/graphics/cairo/ImageCairo.cpp:
        (WebCore::BitmapImage::draw):
        (WebCore::Image::drawPattern):
        * platform/graphics/cairo/ImageSourceCairo.cpp:
        (WebCore::ImageSource::setData):
        * platform/graphics/gtk/ImageGtk.cpp:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@28345 268f45cc-cd09-0410-ab3c-d52691b4dbfc