Fix missing declaration for local variable in interop.js

pkg/browser/lib/interop.js

 // 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 JS interoperability
 // ---------------------------------------------------------------------------
 function SendPortSync() {
 }
 
@@ skipping 439 matching lines @@
     var port = message[2];
     // TODO(vsm): Add a more robust check for a local SendPortSync.
     if ("receivePort" in port) {
       // Local object.
       return proxiedObjectTable.get(id);
     } else {
       // Remote object.
       if (proxiedObjectTable.contains(id)) {
         return proxiedObjectTable.get(id);
       }
-      proxy = new DartObject(id, port);
+      var proxy = new DartObject(id, port);
       proxiedObjectTable.add(proxy, id);
       return proxy;
     }
   }
 
   // Remote handler to construct a new JavaScript object given its
   // serialized constructor and arguments.
   function construct(args) {
     args = args.map(deserialize);
     var constructor = args[0];
@@ skipping 57 matching lines @@
     port.receive(f);
     window.registerPort(name, port.toSendPort());
   }
 
   makeGlobalPort('dart-js-context', context);
   makeGlobalPort('dart-js-create', construct);
   makeGlobalPort('dart-js-instanceof', proxyInstanceof);
   makeGlobalPort('dart-js-delete-property', proxyDeleteProperty);
   makeGlobalPort('dart-js-convert', proxyConvert);
 })();