a === b -> identical(a, b)

samples/swarm/swarm_ui_lib/base/AnimationScheduler.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 typedef void AnimationCallback(num currentTime);
 
 class CallbackData {
   final AnimationCallback callback;
   final num minTime;
   int id;
 
   static int _nextId;
 
-  bool ready(num time) => minTime === null || minTime <= time;
+  bool ready(num time) => minTime == null || minTime <= time;
 
   CallbackData(this.callback, this.minTime) {
     // TODO(jacobr): static init needs cleanup, see http://b/4161827
-    if (_nextId === null) {
+    if (_nextId == null) {
       _nextId = 1;
     }
     id = _nextId++;
   }
 }
 
 /**
  * Animation scheduler implementing the functionality provided by
  * [:window.requestAnimationFrame:] for platforms that do not support it
  * or support it badly.  When multiple UI components are animating at once,
@@ skipping 46 matching lines @@
   int requestAnimationFrame(AnimationCallback callback,
                             [Element element = null,
                              num minTime = null]) {
     final callbackData = new CallbackData(callback, minTime);
     _requestAnimationFrameHelper(callbackData);
     return callbackData.id;
   }
 
   void _requestAnimationFrameHelper(CallbackData callbackData) {
     _callbacks.add(callbackData);
-    if (_intervalId === null) {
+    if (_intervalId == null) {
       _setupInterval();
     }
   }
 
   void _setupInterval() {
     // Assert that we never schedule multiple frames at once.
-    assert(_intervalId === null);
+    assert(_intervalId == null);
     if (USE_INTERVALS) {
       _intervalId = window.setInterval(_step, MS_PER_FRAME);
     } else {
       if (_webkitAnimationFrameMaybeAvailable) {
         try {
           // TODO(jacobr): passing in document should not be required.
           _intervalId = window.webkitRequestAnimationFrame(
               (int ignored) { _step(); });
               // TODO(jacobr) fix this odd type error.
         } catch (e) {
@@ skipping 54 matching lines @@
     _frameCount++;
     if (_isMobileSafari) {
       // Hack to work around an iOS bug where sometimes animations do not
       // render if only webkit transforms were modified.
       // TODO(jacobr): find a cleaner workaround.
       int offset = _frameCount % 2;
       _safariHackStyle.left = '${offset}px';
     }
   }
 }