Rename unsubscribe to cancel.

tests/lib/async/future_test.dart

 // Copyright (c) 2012, 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:async';
 import 'dart:isolate';
 
 testFutureAsStreamCompleteAfter() {
   var completer = new Completer();
   bool gotValue = false;
   var port = new ReceivePort();
-  completer.future.asStream().subscribe(
-      onData: (data) {
+  completer.future.asStream().listen(
+      (data) {
         Expect.isFalse(gotValue);
         gotValue = true;
         Expect.equals("value", data);
       },
       onDone: () {
         Expect.isTrue(gotValue);
         port.close();
       });
   completer.complete("value");
 }
 
 testFutureAsStreamCompleteBefore() {
   var completer = new Completer();
   bool gotValue = false;
   var port = new ReceivePort();
   completer.complete("value");
-  completer.future.asStream().subscribe(
-      onData: (data) {
+  completer.future.asStream().listen(
+      (data) {
         Expect.isFalse(gotValue);
         gotValue = true;
         Expect.equals("value", data);
       },
       onDone: () {
         Expect.isTrue(gotValue);
         port.close();
       });
 }
 
 testFutureAsStreamCompleteImmediate() {
   bool gotValue = false;
   var port = new ReceivePort();
-  new Future.immediate("value").asStream().subscribe(
-      onData: (data) {
+  new Future.immediate("value").asStream().listen(
+      (data) {
         Expect.isFalse(gotValue);
         gotValue = true;
         Expect.equals("value", data);
       },
       onDone: () {
         Expect.isTrue(gotValue);
         port.close();
       });
 }
 
 testFutureAsStreamCompleteErrorAfter() {
   var completer = new Completer();
   bool gotError = false;
   var port = new ReceivePort();
-  completer.future.asStream().subscribe(
-      onData: (data) {
+  completer.future.asStream().listen(
+      (data) {
         Expect.fail("Unexpected data");
       },
       onError: (error) {
         Expect.isFalse(gotError);
         gotError = true;
         Expect.equals("error", error.error);
       },
       onDone: () {
         Expect.isTrue(gotError);
         port.close();
       });
   completer.completeError("error");
 }
 
 testFutureAsStreamWrapper() {
   var completer = new Completer();
   bool gotValue = false;
   var port = new ReceivePort();
   completer.complete("value");
   completer.future
       .catchError((_) { throw "not possible"; })  // Returns a future wrapper.
-      .asStream().subscribe(
-        onData: (data) {
+      .asStream().listen(
+        (data) {
           Expect.isFalse(gotValue);
           gotValue = true;
           Expect.equals("value", data);
         },
         onDone: () {
           Expect.isTrue(gotValue);
           port.close();
         });
 }
 
 main() {
   testFutureAsStreamCompleteAfter();
   testFutureAsStreamCompleteBefore();
   testFutureAsStreamCompleteImmediate();
   testFutureAsStreamCompleteErrorAfter();
   testFutureAsStreamWrapper();
 }