Maintain referential integrity of proxy instances in dart:js

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.
 
 /**
  * The js.dart library provides simple JavaScript invocation from Dart that
  * works on both Dartium and on other modern browsers via Dart2JS.
  *
  * It provides a model based on scoped [JsObject] objects.  Proxies give Dart
  * code access to JavaScript objects, fields, and functions as well as the
@@ skipping 224 matching lines @@
   }
 }
 
 /// Marker class used to indicate it is serializable to js. If a class is a
 /// [Serializable] the "toJs" method will be called and the result will be used
 /// as value.
 abstract class Serializable<T> {
   T toJs();
 }
 
-// A table to managed local Dart objects that are proxied in JavaScript.
+// A table to managed local Dart objects that are proxied in JavaScript,
+// or proxies to JavaScript objects.
 class _ProxiedObjectTable {
   // Debugging name.
   final String _name;
 
   // Generator for unique IDs.
   int _nextId;
 
   // Table of IDs to Dart objects.
   final Map<String, Object> _registry;
 
@@ skipping 20 matching lines @@
           throw 'Invocation unsupported on non-function Dart proxies';
         }
       } catch (e) {
         // TODO(vsm): callSync should just handle exceptions itself.
         return ['throws', '$e'];
       }
     });
   }
 
   // Adds a new object to the table and return a new ID for it.
-  String add(x) {
+  String add(x, {String id}) {
     // TODO(vsm): Cache x and reuse id.
-    final id = '$_name-${_nextId++}';
+    id = (id != null) ? id : '$_name-${_nextId++}';
     _registry[id] = x;
     return id;
   }
 
   // Gets an object by ID.
   Object get(String id) {
     return _registry[id];
   }
 
   // Gets the current number of objects kept alive by this table.
@@ skipping 41 matching lines @@
 }
 
 _deserialize(var message) {
   deserializeFunction(message) {
     var id = message[1];
     var port = message[2];
     if (port == _proxiedObjectTable.sendPort) {
       // Local function.
       return _proxiedObjectTable.get(id);
     } else {
-      // Remote function.  Forward to its port.
-      return new JsFunction._internal(port, id);
+      // Remote function.
+      var jsFunction = _proxiedObjectTable.get(id);
+      if (jsFunction == null) {
+        jsFunction = new JsFunction._internal(port, id);
+        _proxiedObjectTable.add(jsFunction, id: id);
+      }
+      return jsFunction;
     }
   }
 
   deserializeObject(message) {
     var id = message[1];
     var port = message[2];
     if (port == _proxiedObjectTable.sendPort) {
       // Local object.
       return _proxiedObjectTable.get(id);
     } else {
       // Remote object.
-      return new JsObject._internal(port, id);
+      var jsObject = _proxiedObjectTable.get(id);
+      if (jsObject == null) {
+        jsObject = new JsObject._internal(port, id);
+        _proxiedObjectTable.add(jsObject, id: id);
+      }
+      return jsObject;
     }
   }
 
   if (message == null) {
     return null;  // Convert undefined to null.
   } else if (message is String ||
              message is num ||
              message is bool) {
     // Primitives are passed directly through.
     return message;
   } else if (message is SendPortSync) {
     // Serialized type.
     return message;
   }
   var tag = message[0];
   switch (tag) {
     case 'funcref': return deserializeFunction(message);
     case 'objref': return deserializeObject(message);
   }
   throw 'Unsupported serialized data: $message';
 }