Improve Dart Debugger performance and robustness by creating Dart wrappers using the standard SetNa…

Source/bindings/dart/DartDOMWrapper.h

Index: Source/bindings/dart/DartDOMWrapper.h
diff --git a/Source/bindings/dart/DartDOMWrapper.h b/Source/bindings/dart/DartDOMWrapper.h
index a7c6cc080495f19a290c9d088f4ec70b7a0c28a0..2133508bcd6883edafc891052ad61fa97c6d7ba9 100644
--- a/Source/bindings/dart/DartDOMWrapper.h
+++ b/Source/bindings/dart/DartDOMWrapper.h
@@ -188,8 +188,12 @@ private:
     {
         intptr_t value;
         Dart_Handle result = Dart_GetNativeInstanceField(wrapper, index, &value);
-        ASSERT(!Dart_IsError(result));
-        UNUSED_PARAM(result);
+        // FIXME: the fact that we return 0 on error rather than asserting is
+        // somewhat of a hack. We currently make this method return 0 because
+        // we reuse this method to verify that objects are actually native
+        // Node objects rather than objects that implement the Node interface.
+        if (Dart_IsError(result))
+            return 0;
         return reinterpret_cast<void*>(value);
     }