Preserve identity of Dart wrappers on DOM objects

sdk/lib/js/dartium/js_dartium.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Support for interoperating with JavaScript.
  *
  * This library provides access to JavaScript objects from Dart, allowing
  * Dart code to get and set properties, and call methods of JavaScript objects
  * and invoke JavaScript functions. The library takes care of converting
@@ skipping 471 matching lines @@
 /**
  * Proxies a JavaScript object to Dart.
  *
  * The properties of the JavaScript object are accessible via the `[]` and
  * `[]=` operators. Methods are callable via [callMethod].
  */
 class JsObject extends NativeFieldWrapperClass2 {
   JsObject.internal();
 
   /**
+   * If this JsObject is wrapped, e.g. DOM objects, then we can save the
+   * wrapper here and preserve its identity.
+   */
+  var wrapper;

[Jacob, 2015/10/01 21:07:47]

this needs to be private

+
+  /**
    * Constructs a new JavaScript object from [constructor] and returns a proxy
    * to it.
    */
   factory JsObject(JsFunction constructor, [List arguments]) {
     try {
       return _create(constructor, arguments);
     } catch (e) {
       // Re-throw any errors (returned as a string) as a DomException.
       throw new html.DomException.jsInterop(e);
     }
@@ skipping 361 matching lines @@
 
 /**
  * Returns a method that can be called with an arbitrary number (for n less
  * than 11) of arguments without violating Dart type checks.
  */
 Function _wrapAsDebuggerVarArgsFunction(JsFunction jsFunction) =>
     ([a1 = _UNDEFINED, a2 = _UNDEFINED, a3 = _UNDEFINED, a4 = _UNDEFINED,
         a5 = _UNDEFINED, a6 = _UNDEFINED, a7 = _UNDEFINED, a8 = _UNDEFINED,
         a9 = _UNDEFINED, a10 = _UNDEFINED]) => jsFunction._applyDebuggerOnly(
             _stripUndefinedArgs([a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]));