Do not create scrollbars if the subtree is invisible.

Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp

Index: Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
diff --git a/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp b/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
index a81670428299823469018edffe6d78998cf4a5be..0952bbe6d15e5477e55d00173cbf0fec0c0f93a4 100644
--- a/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
+++ b/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
@@ -1286,6 +1286,12 @@ bool CompositedDeprecatedPaintLayerMapping::toggleScrollbarLayerIfNeeded(OwnPtr<
 
 bool CompositedDeprecatedPaintLayerMapping::updateOverflowControlsLayers(bool needsHorizontalScrollbarLayer, bool needsVerticalScrollbarLayer, bool needsScrollCornerLayer, bool needsAncestorClip)
 {
+    // If the subtree is invisible, we don't actually need scrollbar layers.
+    bool invisible = m_owningLayer.subtreeIsInvisible();
+    needsHorizontalScrollbarLayer &= !invisible;
+    needsVerticalScrollbarLayer &= !invisible;
+    needsScrollCornerLayer &= !invisible;
+
     bool horizontalScrollbarLayerChanged = toggleScrollbarLayerIfNeeded(m_layerForHorizontalScrollbar, needsHorizontalScrollbarLayer, CompositingReasonLayerForHorizontalScrollbar);
     bool verticalScrollbarLayerChanged = toggleScrollbarLayerIfNeeded(m_layerForVerticalScrollbar, needsVerticalScrollbarLayer, CompositingReasonLayerForVerticalScrollbar);
     bool scrollCornerLayerChanged = toggleScrollbarLayerIfNeeded(m_layerForScrollCorner, needsScrollCornerLayer, CompositingReasonLayerForScrollCorner);