update3dRenderingContext is 13.5% of GraphicsLayerUpdater::rebuildTree

Source/core/rendering/compositing/CompositedLayerMapping.cpp

Index: Source/core/rendering/compositing/CompositedLayerMapping.cpp
diff --git a/Source/core/rendering/compositing/CompositedLayerMapping.cpp b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
index 592739d51bfde55c970559e0f205bcec517f5235..97b7497e5d58a0b6ef2f10b1c06ab2f6ef87702b 100644
--- a/Source/core/rendering/compositing/CompositedLayerMapping.cpp
+++ b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
@@ -1273,7 +1273,7 @@ void CompositedLayerMapping::updateShouldFlattenTransform()
 {
     // All CLM-managed layers that could affect a descendant layer should update their
     // should-flatten-transform value (the other layers' transforms don't matter here).
-    UpdateShouldFlattenTransformFunctor functor = { m_owningLayer.shouldFlattenTransform() };
+    UpdateShouldFlattenTransformFunctor functor = { !m_owningLayer.shouldPreserve3D() };
     ApplyToGraphicsLayersMode mode = ApplyToCoreLayers;
     ApplyToGraphicsLayers(this, functor, mode);
 }