Support new named arguments.

tests/html/mutationobserver_test.dart

Index: tests/html/mutationobserver_test.dart
diff --git a/tests/html/mutationobserver_test.dart b/tests/html/mutationobserver_test.dart
index 948d0c61f16b58ffa9282fe983aad102d6727970..b2b0ec410d29075c3a3c376a6fd29d77e902869e 100644
--- a/tests/html/mutationobserver_test.dart
+++ b/tests/html/mutationobserver_test.dart
@@ -61,7 +61,8 @@ main() {
         var div2 = new DivElement();
         var mutationObserver = new MutationObserver(
             mutationCallback(2, orderedEquals([div1, div2])));
-        mutationObserver.observe(container, childList: true);
+        // OPTIONALS mutationObserver.observe(container, childList: true);
+        mutationObserver.observe(container, {}, true);
 
         container.nodes.add(div1);
         container.nodes.add(div2);
@@ -73,7 +74,8 @@ main() {
         var div2 = new DivElement();
         var mutationObserver =
             new MutationObserver(mutationCallback(1, orderedEquals([div1])));
-        mutationObserver.observe(container, childList: true);
+        // OPTIONALS mutationObserver.observe(container, childList: true);
+        mutationObserver.observe(container, {}, true);
 
         container.nodes.add(div1);
         div1.nodes.add(div2);
@@ -99,7 +101,8 @@ main() {
         var div2 = new DivElement();
         var mutationObserver = new MutationObserver(
             mutationCallback(2, orderedEquals([div1, div2])));
-        mutationObserver.observe(container, childList: true, subtree: true);
+        // OPTIONALS mutationObserver.observe(container, childList: true, subtree: true);
+        mutationObserver.observe(container, {}, true, null, null, true);
 
         container.nodes.add(div1);
         div1.nodes.add(div2);