update elements and fix some bugs

test/iron_overlay_behavior_test.dart

 @TestOn('browser')
 library polymer_elements.test.iron_overlay_behavior_test;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:html';
 import 'dart:js';
 import 'package:polymer_interop/polymer_interop.dart';
 import 'package:polymer/polymer.dart';
 import 'package:test/test.dart';
 import 'package:web_components/web_components.dart';
 import 'common.dart';
 import 'fixtures/test_overlay.dart';
 
 runAfterOpen(overlay, cb) {
-  overlay.on['iron-overlay-opened'].take(1).listen((_) {
+  overlay.on['iron-overlay-opened'].take(1).listen((_) async {
+    await wait(1);
     cb();
   });
   overlay.open();
 }
 
 main() async {
   await initPolymer();
 
   group('basic overlay tests', () {
     TestOverlay overlay;
@@ skipping 93 matching lines @@
             document.activeElement,
             reason: '<button autofocus> is focused');
         done.complete();
       });
       return done.future;
     });
 
     test('cancel an overlay by clicking outside', () {
       var done = new Completer();
       runAfterOpen(overlay, () {
-        overlay.on['iron-overlay-closed'].take(1).listen((event) {
+        overlay.on['iron-overlay-canceled'].first.then((_) {
+          done.complete();
+        });
+        fireEvent('click', null, document);
+      });
+      return done.future;
+    });
+
+    test('close an overlay by clicking outside', () {
+      var done = new Completer();
+      runAfterOpen(overlay, () {
+        overlay.on['iron-overlay-closed'].first.then((event) {
           expect(event.detail['canceled'], isTrue,
               reason: 'overlay is canceled');
           done.complete();
         });
         fireEvent('click', null, document);
       });
       return done.future;
     });
 
+    test('cancel event can be prevented', () {
+      var done = new Completer();
+      runAfterOpen(overlay, () {
+        overlay.on['iron-overlay-canceled'].first.then((event) {
+          event.preventDefault();
+        });
+        var listener =
+          overlay.on['iron-overlay-closed'].listen((event) {
+            throw 'iron-overlay-closed should not fire';
+          });
+        fireEvent('click', null, document);
+        wait(10).then((_) {
+          listener.cancel();
+          done.complete();
+        });
+      });
+      return done.future;
+    });
+
     test('cancel an overlay with esc key', () {
       var done = new Completer();
       runAfterOpen(overlay, () {
+        overlay.on['iron-overlay-canceled'].first.then((event) {
+          done.complete();
+        });
+        fireEvent('keydown', {
+          'keyCode': 27
+        }, document);
+      });
+    });
+
+    test('close an overlay with esc key', () {
+      var done = new Completer();
+      runAfterOpen(overlay, () {
         overlay.on['iron-overlay-closed'].take(1).listen((event) {
           expect(event.detail['canceled'], isTrue,
               reason: 'overlay is canceled');
           done.complete();
         });
         fireEvent('keydown', {'keyCode': 27}, document);
       });
       return done.future;
     });
 
@@ skipping 145 matching lines @@
       expect(overlay.getAttribute('aria-hidden'), isNull,
           reason: 'overlay does not have aria-hidden attribute');
       return wait(1).then((_) {
         overlay.close();
         expect(overlay.getAttribute('aria-hidden'), 'true',
           reason: 'overlay has aria-hidden="true"');
       });
     });
   });
 }