Revert "Add Isolate.kill()."

tests/isolate/ping_pause_test.dart

 // Copyright (c) 2014, 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.
 
 import "dart:isolate";
 import "dart:async";
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 
 isomain1(replyPort) {
@@ skipping 23 matching lines @@
       echoPort.send(4);
       echoPort.send(3);
       Capability resume = isolate.pause();
       var pingPort = new RawReceivePort();
       pingPort.handler = (_) {
         Expect.isTrue(result.length <= 2);
         echoPort.send(0);
         isolate.resume(resume);
         pingPort.close();
       };
-      isolate.ping(pingPort.sendPort, Isolate.BEFORE_NEXT_EVENT);
+      isolate.ping(pingPort.sendPort, Isolate.PING_CONTROL);
       echoPort.send(2);
       echoPort.send(1);
     });
   });
 }