Keep a persistent handle for the bindings classes to avoid repeated lookups that involve performing…

Source/bindings/dart/DartDOMData.h

Index: Source/bindings/dart/DartDOMData.h
diff --git a/Source/bindings/dart/DartDOMData.h b/Source/bindings/dart/DartDOMData.h
index 2f6927dc0214e394716dc9653ce0ef7533463b45..2842530dae7f0065a0c069bcbca8cd4fc8c6c4ca 100644
--- a/Source/bindings/dart/DartDOMData.h
+++ b/Source/bindings/dart/DartDOMData.h
@@ -98,6 +98,8 @@ public:
     DartCustomElementMap* customElementMap() { return &m_customElementMap; }
     DartCustomElementMap* customBaseElementMap() { return &m_customBaseElementMap; }
 
+    Vector<Dart_PersistentHandle>* classHandleCache() { return &m_classHandleCache; }
+
 private:
     ScriptExecutionContext* m_scriptExecutionContext;
     bool m_isDOMEnabled;
@@ -118,6 +120,8 @@ private:
     DartIsolateDestructionObservers m_isolateDestructionObservers;
     DartCustomElementMap m_customElementMap;
     DartCustomElementMap m_customBaseElementMap;
+
+    Vector<Dart_PersistentHandle> m_classHandleCache;
 };
 
 }