Rename unsubscribe to cancel.

tests/lib/async/stream_controller_async_test.dart

 // Copyright (c) 2011, 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.
 
 // Test the basic StreamController and StreamController.singleSubscription.
 import 'dart:async';
 import 'dart:isolate';
 import '../../../pkg/unittest/lib/unittest.dart';
 import 'event_helper.dart';
 
@@ skipping 65 matching lines @@
 
   test("Single-subscription StreamController subscription changes", () {
     StreamController c = new StreamController.singleSubscription();
     StreamSink sink = c.sink;
     Stream stream = c.stream;
     int counter = 0;
     var subscription;
     subscription = stream.listen((data) {
       counter += data;
       Expect.throws(() => stream.listen(null), (e) => e is StateError);
-      subscription.unsubscribe();
+      subscription.cancel();
       stream.listen((data) {
         counter += data * 10;
       },
       onDone: expectAsync0(() {
         Expect.equals(1 + 20, counter);
       }));
     });
     sink.add(1);
     sink.add(2);
     sink.close();
@@ skipping 21 matching lines @@
   // Test subscription changes while firing.
   test("Single-subscription StreamController subscription changes while firing",
        () {
     StreamController c = new StreamController.singleSubscription();
     StreamSink sink = c.sink;
     Stream stream = c.stream;
     int counter = 0;
     var subscription = stream.listen(null);
     subscription.onData(expectAsync1((data) {
       counter += data;
-      subscription.unsubscribe();
+      subscription.cancel();
       stream.listen((data) {
         counter += 10 * data;
       },
       onDone: expectAsync0(() {
         Expect.equals(1 + 20 + 30 + 40 + 50, counter);
       }));
       Expect.throws(() => stream.listen(null), (e) => e is StateError);
     }));
     sink.add(1); // seen by stream 1
     sink.add(2); // seen by stream 10 and 100
@@ skipping 250 matching lines @@
     actualEvents.resume();
   });
 }
 
 main() {
   testController();
   testSingleController();
   testExtraMethods();
   testPause();
 }