Make sure ScriptWrappables have a wrapper before calling setReference()

third_party/WebKit/Source/bindings/core/v8/DOMWrapperWorld.cpp

Index: third_party/WebKit/Source/bindings/core/v8/DOMWrapperWorld.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/DOMWrapperWorld.cpp b/third_party/WebKit/Source/bindings/core/v8/DOMWrapperWorld.cpp
index caf91073a0b13905e80c6cbb87fafe0eb6b9480c..293a277cadf5419117b0a55a07074e6e6ff7a164 100644
--- a/third_party/WebKit/Source/bindings/core/v8/DOMWrapperWorld.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/DOMWrapperWorld.cpp
@@ -160,7 +160,8 @@ void DOMWrapperWorld::markWrappersInAllWorlds(ScriptWrappable* scriptWrappable,
 void DOMWrapperWorld::setWrapperReferencesInAllWorlds(const v8::Persistent<v8::Object>& parent, ScriptWrappable* scriptWrappable, v8::Isolate* isolate)
 {
     // Marking for the main world
-    scriptWrappable->setReference(parent, isolate);
+    if (scriptWrappable->containsWrapper())
+        scriptWrappable->setReference(parent, isolate);
     if (!isMainThread())
         return;
     WorldMap& isolatedWorlds = isolatedWorldMap();