Revert "Patched in Dartium JsInterop"

tools/dom/templates/html/impl/impl_MutationObserver.darttemplate

Index: tools/dom/templates/html/impl/impl_MutationObserver.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_MutationObserver.darttemplate b/tools/dom/templates/html/impl/impl_MutationObserver.darttemplate
index 079ca0f1e3c5a6e9d71825de9ddf3f915f93f24c..d45e98a0e1c7b0e07fee7b6c73b57d9afb02febd 100644
--- a/tools/dom/templates/html/impl/impl_MutationObserver.darttemplate
+++ b/tools/dom/templates/html/impl/impl_MutationObserver.darttemplate
@@ -21,8 +21,14 @@ $endif
 $if DARTIUM
   @DocsEditable()
   $if JSINTEROP
-  static MutationObserver _create(callback) => wrap_jso(_blink.BlinkMutationObserver.instance.constructorCallback_1_((mutations, observer) {
-    callback(mutations, wrap_jso(observer));
+  static MutationObserver _create(callback) => wrap_jso(_blink.BlinkMutationObserver.instance.constructorCallback_1_((List<MutationRecord> mutations, MutationObserver observer) {
+      var wrapped_mutations = [];
+      for (var mutation in mutations) {
+        // Wrap the Javascript object for each MutationRecord.
+        wrapped_mutations.add(wrap_jso(mutation));
+      }
+      // Wrap the MutationObserver too.
+      callback(wrapped_mutations, wrap_jso(observer));
   }));
   $else
   static MutationObserver _create(callback) => _blink.BlinkMutationObserver.instance.constructorCallback_1_(callback);