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

samples/swarm/swarm_ui_lib/base/Size.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.
 
 /**
  * A utility class for representing two-dimensional sizes.
  */
 class Size {
   num width;
   num height;
 
   Size(num this.width, num this.height) {
   }
 
   bool operator ==(Size other) {
-    return other !== null && width == other.width && height == other.height;
+    return other != null && width == other.width && height == other.height;
   }
 
   /**
    * Returns the area of the size (width * height).
    */
   num area() {
     return width * height;
   }
 
   /**
@@ skipping 102 matching lines @@
   }
 
   /**
    * Returns a nice string representing size.
    * Returns in the form (50 x 73).
    */
   String toString() {
     return "(${width} x ${height})";
   }
 }