Naive fix of a call on a nil object in CompositedLayerMapping::containingSquashedLayer.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index 0940c3e15bb0ed52846c2db078e86417316964b1..ebe400f573dabc4f76ab52aa00f487e94387c851 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -2610,6 +2610,8 @@ const GraphicsLayerPaintInfo* CompositedLayerMapping::containingSquashedLayer(
     const LayoutObject* layoutObject,
     const Vector<GraphicsLayerPaintInfo>& layers,
     unsigned maxSquashedLayerIndex) {
+  if (!layoutObject)
+    return nullptr;
   for (size_t i = 0; i < layers.size() && i < maxSquashedLayerIndex; ++i) {
     if (layoutObject->isDescendantOf(layers[i].paintLayer->layoutObject()))
       return &layers[i];