Use a boolean hasCompositedLayerMapping() accessor instead of the pointer

Source/core/rendering/svg/SVGRenderingContext.cpp

Index: Source/core/rendering/svg/SVGRenderingContext.cpp
diff --git a/Source/core/rendering/svg/SVGRenderingContext.cpp b/Source/core/rendering/svg/SVGRenderingContext.cpp
index f308081f724d125600cc4776d975212d741892bb..bba0e06ef575ad306aa4f50a78434e988007257a 100644
--- a/Source/core/rendering/svg/SVGRenderingContext.cpp
+++ b/Source/core/rendering/svg/SVGRenderingContext.cpp
@@ -228,7 +228,9 @@ void SVGRenderingContext::calculateTransformationToOutermostCoordinateSystem(con
         // We can stop at compositing layers, to match the backing resolution.
         // FIXME: should we be computing the transform to the nearest composited layer,
         // or the nearest composited layer that does not paint into its ancestor?
-        if (layer->compositedLayerMapping())
+        // I think this is the nearest composited ancestor since we will inherit its
+        // transforms in the composited layer tree.
+        if (layer->hasCompositedLayerMapping())
             break;
 
         layer = layer->parent();