wrap_jso should wrap JsArray as well, not always call wrap on its contents

tools/dom/templates/html/dartium/html_dartium.darttemplate

Index: tools/dom/templates/html/dartium/html_dartium.darttemplate
diff --git a/tools/dom/templates/html/dartium/html_dartium.darttemplate b/tools/dom/templates/html/dartium/html_dartium.darttemplate
index cb5e7dd2037f7cc3338f5fb6a261635e2a1e43df..e33b195264cdafaffb5da53c235395c0ec38ad21 100644
--- a/tools/dom/templates/html/dartium/html_dartium.darttemplate
+++ b/tools/dom/templates/html/dartium/html_dartium.darttemplate
@@ -404,6 +404,12 @@ wrap_jso(jsObject) {
       return wrapper;
     }
 
+    if (jsObject is js.JsArray) {
+      var wrappingList = new _DartHtmlWrappingList(jsObject);
+      js.setDartHtmlWrapperFor(jsObject, wrappingList);
+      return wrappingList;
+    }
+
     // Try the most general type conversions on it.
     // TODO(alanknight): We may be able to do better. This maintains identity,
     // which is useful, but expensive. And if we nest something that only
@@ -549,6 +555,22 @@ convertDartToNative_List(List input) => new js.JsArray()..addAll(input);
 // Conversion function place holder (currently not used in dart2js or dartium).
 List convertDartToNative_StringArray(List<String> input) => input;
 
+/**
+ * Wraps a JsArray and will call wrap_jso on its entries.
+ */
+class _DartHtmlWrappingList extends ListBase {
+  _DartHtmlWrappingList(this._basicList);
+
+  final js.JsArray _basicList;
+
+  operator [](int index) => wrap_jso(_basicList[index]);
+
+  operator []=(int index, value) => _basicList[index] = unwrap_jso(value);
+
+  int get length => _basicList.length;
+  int set length(int newLength) => _basicList.length = newLength;
+}
+
 $else
 class JsoNativeFieldWrapper extends NativeFieldWrapperClass2 {}