Missed adding the isExternal property to all VM MethodMirror subclasses.

sdk/lib/html/html_common/conversions_dartium.dart

Index: sdk/lib/html/html_common/conversions_dartium.dart
diff --git a/sdk/lib/html/html_common/conversions_dartium.dart b/sdk/lib/html/html_common/conversions_dartium.dart
index 22738eae6fa2a001fc93c350f58c0890ffb0fd5b..2403387b4e608e457e43e88cf080c08d76d2b535 100644
--- a/sdk/lib/html/html_common/conversions_dartium.dart
+++ b/sdk/lib/html/html_common/conversions_dartium.dart
@@ -236,6 +236,13 @@ wrap_jso_no_SerializedScriptvalue(jsObject) {
       return wrapper;
     }
 
+    // TODO(jacobr): auomatically wrapping JsArray here is fundamentally broken
+    // as it hijacks adding custom methods on JS Array classes as part of the
+    // new typed DartJsInterop.
+    // To make this work we really need to make DartHtmlWrappingList extend
+    // JsArrayImpl. Fixing this issue needs to be part of a broader refactor
+    // that allows calling custom typed JS interop methods on all dart:html
+    // classes.
     if (jsObject is js.JsArray) {
       var wrappingList = new DartHtmlWrappingList(jsObject);
       js.setDartHtmlWrapperFor(jsObject, wrappingList);
@@ -380,7 +387,7 @@ class DartHtmlWrappingList extends ListBase implements NativeFieldWrapperClass2
 
   final js.JsArray blink_jsObject;
 
-  operator [](int index) => wrap_jso(js.JsNative.getArrayIndex(blink_jsObject, index));
+  operator [](int index) => wrap_jso_no_SerializedScriptvalue(js.JsNative.getArrayIndex(blink_jsObject, index));
 
   operator []=(int index, value) => blink_jsObject[index] = value;