Remove PostAttachCallbacks and replace with something more specialized

Source/core/rendering/RenderLayerFilterInfo.cpp

Index: Source/core/rendering/RenderLayerFilterInfo.cpp
diff --git a/Source/core/rendering/RenderLayerFilterInfo.cpp b/Source/core/rendering/RenderLayerFilterInfo.cpp
index 473e9eb6ce2d18c66af1e9617572ba4cdd7a0d1b..8a6e2b4bed817f02a18c9eca0a27dee4ffe3e74f 100644
--- a/Source/core/rendering/RenderLayerFilterInfo.cpp
+++ b/Source/core/rendering/RenderLayerFilterInfo.cpp
@@ -104,6 +104,10 @@ void RenderLayerFilterInfo::setRenderer(PassRefPtr<FilterEffectRenderer> rendere
 void RenderLayerFilterInfo::notifyFinished(Resource*)
 {
     RenderObject* renderer = m_layer->renderer();
+    // FIXME: This caller of scheduleLayerUpdate() is not correct. It's using the layer update
+    // system to trigger a RenderLayer to go through the filter updating logic, but that might not
+    // even happen if this element is style sharing and RenderObject::setStyle() returns early.
+    // Filters need to find a better way to hook into the system.
     toElement(renderer->node())->scheduleLayerUpdate();
     renderer->repaint();
 }