dom test: fix test after change in isolate library.

client/tests/client/dom/IsolatesTest.dart

 #library('IsolatesTest');
 #import('../../../testing/unittest/unittest.dart');
 #import('dart:dom');
 #import('dart:json');
-#import('dart:isolate');
+#import('dart:isolate', prefix:'isolate');
 
-class PingPongIsolate extends Isolate {
+class PingPongIsolate extends isolate.Isolate {
   PingPongIsolate() : super.heavy();
 
   void main() {
     bool wasThrown = false;
     try {
       window.alert('Test');
     } catch(final e) {
       wasThrown = true;
     }
     // If wasn't thrown, do not listen to messages to make test fail.
     if (!wasThrown) {
       return;
     }
 
     // Check that JSON library was loaded to isolate.
     JSON.stringify([1, 2, 3]);
 
     port.receive((message, replyTo) {

[Siggi Cherem (dart-lang), 2012/02/29 01:39:27]

there is a port in the super class and one in the library (recently added). This
test broke because this [port] was resolved to the library definition.

       replyTo.send(responseFor(message), null);
     });
   }
 
   static String responseFor(message) => 'response for $message';
 }
 
 main() {
   forLayoutTests();
   asyncTest('IsolateSpawn', 1, () {
-    new PingPongIsolate().spawn().then((SendPort port) {
+    new PingPongIsolate().spawn().then((isolate.SendPort port) {
       callbackDone();
     });
   });
   asyncTest('NonDOMIsolates', 1, () {
-    new PingPongIsolate().spawn().then((SendPort port) {
+    new PingPongIsolate().spawn().then((isolate.SendPort port) {
       final msg1 = 'foo';
       final msg2 = 'bar';
       port.call(msg1).receive((response, _) {
         Expect.equals(PingPongIsolate.responseFor(msg1), response);
         port.call(msg2).receive((response, _) {
           Expect.equals(PingPongIsolate.responseFor(msg2), response);
           callbackDone();
         });
       });
     });
   });
 }