Remove old isolate API and update all code in the repository to use

tests/html/isolates_test.dart

 #library('IsolatesTest');
 #import('../../lib/unittest/unittest.dart');
 #import('../../lib/unittest/html_config.dart');
 #import('dart:html');
 #import('dart:json');
 #import('dart:isolate', prefix:'isolate');
 
-class PingPongIsolate extends isolate.Isolate {
-  PingPongIsolate() : super.heavy();
+String responseFor(message) => 'response for $message';
 
-  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) {
-      replyTo.send(responseFor(message), null);
-    });
+void isolateEntry() {
+  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;
   }
 
-  static String responseFor(message) => 'response for $message';
+  // Check that JSON library was loaded to isolate.
+  JSON.stringify([1, 2, 3]);
+
+  isolate.port.receive((message, replyTo) {
+    replyTo.send(responseFor(message), null);
+  });
 }
 
 main() {
   useHtmlConfiguration();
   test('IsolateSpawn', () {
-    new PingPongIsolate().spawn().then(expectAsync1((isolate.SendPort port) {
-    }));
+    isolate.spawnFunction(isolateEntry);
   });
   test('NonDOMIsolates', () {
     var callback = expectAsync0((){});
-    new PingPongIsolate().spawn().then((isolate.SendPort port) {
+    var port = isolate.spawnFunction(isolateEntry);
+    final msg1 = 'foo';
+    final msg2 = 'bar';
+    port.call(msg1).then((response) {
       guardAsync(() {
-        final msg1 = 'foo';
-        final msg2 = 'bar';
-        port.call(msg1).then((response) {
+        Expect.equals(responseFor(msg1), response);
+        port.call(msg2).then((response) {
           guardAsync(() {
-            Expect.equals(PingPongIsolate.responseFor(msg1), response);
-            port.call(msg2).then((response) {
-              guardAsync(() {
-                Expect.equals(PingPongIsolate.responseFor(msg2), response);
-                callback();
-              });
-            });
+            Expect.equals(responseFor(msg2), response);
+            callback();
           });
         });
       });
     });
   });
 }