Fix for CSS reference effects when the filter renderer is lazy attached (e.g., assigned via innerHTML).

If the SVGFilterElement does not have a renderer yet, queue up adding client
RenderLayers until we created the renderer. This is take two on senorblanco's
patch https://chromiumcodereview.appspot.com/23672007 which got rolled out due
to a use-after-free.

In this version of the patch, hold onto RefPtr<Node> instead of RenderLayers.
This should fix the user-after-free and avoids the DOM needing to know about
RenderLayers.

BUG=272585

Review URL: https://chromiumcodereview.appspot.com/23632008

git-svn-id: svn://svn.chromium.org/blink/trunk@157176 bbb929c8-8fbe-4397-9dbb-9b2b20218538