Don't share same name for js proxies cache.

sdk/lib/js/dart2js/js_dart2js.dart

Index: sdk/lib/js/dart2js/js_dart2js.dart
diff --git a/sdk/lib/js/dart2js/js_dart2js.dart b/sdk/lib/js/dart2js/js_dart2js.dart
index 576cb23451a596c23f569eecca11f7185d2cebbb..f9d2ade91b219837494e8fe692d12cdb30ba7a06 100644
--- a/sdk/lib/js/dart2js/js_dart2js.dart
+++ b/sdk/lib/js/dart2js/js_dart2js.dart
@@ -4,7 +4,7 @@
 
 /**
  * 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
@@ -27,14 +27,14 @@
  * global function `alert()`:
  *
  *     import 'dart:js';
- *     
+ *
  *     main() => context.callMethod('alert', ['Hello from Dart!']);
  *
  * This example shows how to create a [JsObject] from a JavaScript constructor
  * and access its properties:
  *
  *     import 'dart:js';
- *     
+ *
  *     main() {
  *       var object = new JsObject(context['Object']);
  *       object['greeting'] = 'Hello';
@@ -44,7 +44,7 @@
  *     }
  *
  * ## Proxying and automatic conversion
- * 
+ *
  * When setting properties on a JsObject or passing arguments to a Javascript
  * method or function, Dart objects are automatically converted or proxied to
  * JavaScript objects. When accessing JavaScript properties, or when a Dart
@@ -80,7 +80,7 @@
  * `a` and `b` defined:
  *
  *     var jsMap = new JsObject.jsify({'a': 1, 'b': 2});
- * 
+ *
  * This expression creates a JavaScript array:
  *
  *     var jsArray = new JsObject.jsify([1, 2, 3]);
@@ -165,7 +165,7 @@ class JsObject {
    * Use this constructor only if you wish to get access to JavaScript
    * properties attached to a browser host object, such as a Node or Blob, that
    * is normally automatically converted into a native Dart object.
-   * 
+   *
    * An exception will be thrown if [object] either is `null` or has the type
    * `bool`, `num`, or `String`.
    */
@@ -232,7 +232,7 @@ class JsObject {
     }
     return _convertToDart(JS('', '#[#]', _jsObject, property));
   }
-  
+
   /**
    * Sets the value associated with [property] on the proxied JavaScript
    * object.
@@ -410,7 +410,7 @@ class JsArray<E> extends JsObject with ListMixin<E> {
   }
 
   void addAll(Iterable<E> iterable) {
-    var list = (JS('bool', '# instanceof Array', iterable)) 
+    var list = (JS('bool', '# instanceof Array', iterable))
         ? iterable
         : new List.from(iterable);
     callMethod('push', list);
@@ -450,9 +450,28 @@ class JsArray<E> extends JsObject with ListMixin<E> {
   }
 }
 
+// When multiple Dart programs are run in the same page we must make sure that
+// they don't share their Dart wrappers. We use a global (shared) counter in
+// the Object class to assign a unique id to every Dart program.
+int _getAndUpdateDisambiguationId() {
+  const DISAMBIGUATION_PROPERTY_NAME = "__DART_INTEROP_COUNTER_";
+  int counter = JS("int", 'Object[#]||0', DISAMBIGUATION_PROPERTY_NAME);
+  JS("", 'Object[#]=#', DISAMBIGUATION_PROPERTY_NAME, counter + 1);
+  return counter;
+}
+
+final int _disambiguationId = _getAndUpdateDisambiguationId();
+
+// Converts the given string to a v8 internal symbol which is faster.
+String _intern(String str) {
+  return JS("String", "convertToJSSymbol(#)", str);
+}
+
 // property added to a Dart object referencing its JS-side DartObject proxy
-const _DART_OBJECT_PROPERTY_NAME = r'_$dart_dartObject';
-const _DART_CLOSURE_PROPERTY_NAME = r'_$dart_dartClosure';
+final String _DART_OBJECT_PROPERTY_NAME =
+    _intern("_\$dart_dartObject$_disambiguationId");
+final String _DART_CLOSURE_PROPERTY_NAME =
+    _intern("_\$dart_dartObject$_disambiguationId");
 
 // property added to a JS object referencing its Dart-side JsObject proxy
 const _JS_OBJECT_PROPERTY_NAME = r'_$dart_jsObject';