Make length property return useful values for DOM bindings functions

Source/bindings/v8/V8DOMConfiguration.h

Index: Source/bindings/v8/V8DOMConfiguration.h
diff --git a/Source/bindings/v8/V8DOMConfiguration.h b/Source/bindings/v8/V8DOMConfiguration.h
index 82face935ea4e355ff93d6f8b648ccc970bb9e4f..6843974182f622b973be563f61ff4f69994a1fe3 100644
--- a/Source/bindings/v8/V8DOMConfiguration.h
+++ b/Source/bindings/v8/V8DOMConfiguration.h
@@ -102,6 +102,7 @@ public:
         const char* const name;
         v8::InvocationCallback callback;
         v8::InvocationCallback callbackForMainWorld;
+        int length;
     };
 
     static void batchConfigureCallbacks(v8::Handle<v8::ObjectTemplate>, v8::Handle<v8::Signature>, v8::PropertyAttribute, const BatchedMethod*, size_t callbackCount, v8::Isolate*, WrapperWorldType);