Fix const correctness of containerForRepaint

Source/core/rendering/compositing/RenderLayerCompositor.cpp

Index: Source/core/rendering/compositing/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.cpp b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
index b08d68e0f2b22853a6eb1295a4426b0f687db506..3a7d831cbeaa5d7da544c1ca1c981030b3373641 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -629,7 +629,7 @@ void RenderLayerCompositor::repaintOnCompositingChange(RenderLayer* layer)
     if (layer->renderer() != &m_renderView && !layer->renderer()->parent())
         return;
 
-    RenderLayerModelObject* repaintContainer = layer->renderer()->containerForRepaint();
+    const RenderLayerModelObject* repaintContainer = layer->renderer()->containerForRepaint();
     ASSERT(repaintContainer);
     layer->repainter().repaintIncludingNonCompositingDescendants(repaintContainer);
 }