DOM wrappers that are not retained from Dart should be collected.

Source/WebCore/bindings/dart/DartUtilities.cpp

Index: Source/WebCore/bindings/dart/DartUtilities.cpp
diff --git a/Source/WebCore/bindings/dart/DartUtilities.cpp b/Source/WebCore/bindings/dart/DartUtilities.cpp
index 82867ea7794a3e92d4d455e22a98d37249f5e626..e3eb39afcaa60fba4c4630abe2fad0bfde93c050 100644
--- a/Source/WebCore/bindings/dart/DartUtilities.cpp
+++ b/Source/WebCore/bindings/dart/DartUtilities.cpp
@@ -269,6 +269,11 @@ public:
         m_domWindow = document->domWindow();
     }
 
+    ~DartDOMData()
+    {
+        ASSERT(m_domMap.isEmpty());
+    }
+
     PassRefPtr<DartApplicationLoader> applicationLoader() { return m_applicationLoader; }
     ScriptExecutionContext* scriptExecutionContext() { return m_scriptExecutionContext; }
     DOMWindow* domWindow() { return m_domWindow; }
@@ -300,7 +305,7 @@ static DartDOMData* domDataForIsolate(Dart_Isolate isolate)
 
 static DartDOMData* currentDOMData()
 {
-    return domDataForIsolate(DartIsolate::current()->isolate());
+    return domDataForIsolate(Dart_CurrentIsolate());
 }
 
 void DartUtilities::registerDOMIsolate(Dart_Isolate isolate, PassRefPtr<DartApplicationLoader> applicationLoader, ScriptExecutionContext* context)