diff --git a/CHANGELOG.md b/CHANGELOG.md
index 75439f763ec..35da026d4e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,12 +16,6 @@
   * Report a better error when a bind fails because of a bad source address.
   * Handle HTTP header `charset` parameter with empty value.
 
-* `dart:async`
-  * More aggressively returns a Future on Stream.cancel operations.
-    Discourages to return `null` from `cancel`.
-  * Fixes a few bugs where the cancel future wasn't passed through
-    transformations.
-
 ### Strong Mode
 
 *   New feature - an option to disable implicit casts
diff --git a/sdk/lib/async/stream.dart b/sdk/lib/async/stream.dart
index f4abf9aac9c..7661d9ffe99 100644
--- a/sdk/lib/async/stream.dart
+++ b/sdk/lib/async/stream.dart
@@ -232,7 +232,6 @@ abstract class Stream<T> {
         onCancel: () {
           if (timer != null) timer.cancel();
           timer = null;
-          return Future._nullFuture;
         });
     return controller.stream;
   }
@@ -442,7 +441,7 @@ abstract class Stream<T> {
         onListen: onListen,
         onPause: () { subscription.pause(); },
         onResume: () { subscription.resume(); },
-        onCancel: () => subscription.cancel(),
+        onCancel: () { subscription.cancel(); },
         sync: true
       );
     }
@@ -500,7 +499,7 @@ abstract class Stream<T> {
         onListen: onListen,
         onPause: () { subscription.pause(); },
         onResume: () { subscription.resume(); },
-        onCancel: () => subscription.cancel(),
+        onCancel: () { subscription.cancel(); },
         sync: true
       );
     }
@@ -1408,10 +1407,7 @@ abstract class StreamSubscription<T> {
    * the subscription is canceled.
    *
    * Returns a future that is completed once the stream has finished
-   * its cleanup.
-   *
-   * For historical reasons, may also return `null` if no cleanup was necessary.
-   * Returning `null` is deprecated and should be avoided.
+   * its cleanup. May also return `null` if no cleanup was necessary.
    *
    * Typically, futures are returned when the stream needs to release resources.
    * For example, a stream might need to close an open file (as an asynchronous
@@ -1715,7 +1711,7 @@ abstract class StreamTransformer<S, T> {
    *             },
    *             onPause: () { subscription.pause(); },
    *             onResume: () { subscription.resume(); },
-   *             onCancel: () => subscription.cancel(),
+   *             onCancel: () { subscription.cancel(); },
    *             sync: true);
    *           return controller.stream.listen(null);
    *         });
diff --git a/sdk/lib/async/stream_impl.dart b/sdk/lib/async/stream_impl.dart
index cb2e20d0f13..8c9af64bb9e 100644
--- a/sdk/lib/async/stream_impl.dart
+++ b/sdk/lib/async/stream_impl.dart
@@ -188,10 +188,9 @@ class _BufferingStreamSubscription<T> implements StreamSubscription<T>,
     // error or done event pending (waiting for the cancel to be done) discard
     // that event.
     _state &= ~_STATE_WAIT_FOR_CANCEL;
-    if (!_isCanceled) {
-      _cancel();
-    }
-    return _cancelFuture ?? Future._nullFuture;
+    if (_isCanceled) return _cancelFuture;
+    _cancel();
+    return _cancelFuture;
   }
 
   Future/*<E>*/ asFuture/*<E>*/([var/*=E*/ futureValue]) {
@@ -200,14 +199,8 @@ class _BufferingStreamSubscription<T> implements StreamSubscription<T>,
     // Overwrite the onDone and onError handlers.
     _onDone = () { result._complete(futureValue); };
     _onError = (error, stackTrace) {
-      Future cancelFuture = cancel();
-      if (!identical(cancelFuture, Future._nullFuture)) {
-        cancelFuture.whenComplete(() {
-          result._completeError(error, stackTrace);
-        });
-      } else {
-        result._completeError(error, stackTrace);
-      }
+      cancel();
+      result._completeError(error, stackTrace);
     };
 
     return result;
@@ -368,8 +361,7 @@ class _BufferingStreamSubscription<T> implements StreamSubscription<T>,
     if (_cancelOnError) {
       _state |= _STATE_WAIT_FOR_CANCEL;
       _cancel();
-      if (_cancelFuture is Future &&
-          !identical(_cancelFuture, Future._nullFuture)) {
+      if (_cancelFuture is Future) {
         _cancelFuture.whenComplete(sendError);
       } else {
         sendError();
@@ -397,8 +389,7 @@ class _BufferingStreamSubscription<T> implements StreamSubscription<T>,
 
     _cancel();
     _state |= _STATE_WAIT_FOR_CANCEL;
-    if (_cancelFuture is Future &&
-        !identical(_cancelFuture, Future._nullFuture)) {
+    if (_cancelFuture is Future) {
       _cancelFuture.whenComplete(sendDone);
     } else {
       sendDone();
@@ -787,7 +778,7 @@ class _DoneStreamSubscription<T> implements StreamSubscription<T> {
     }
   }
 
-  Future cancel() => Future._nullFuture;
+  Future cancel() => null;
 
   Future/*<E>*/ asFuture/*<E>*/([var/*=E*/ futureValue]) {
     _Future/*<E>*/ result = new _Future/*<E>*/();
@@ -925,7 +916,7 @@ class _BroadcastSubscriptionWrapper<T> implements StreamSubscription<T> {
 
   Future cancel() {
     _stream._cancelSubscription();
-    return Future._nullFuture;
+    return null;
   }
 
   bool get isPaused {
@@ -1041,7 +1032,7 @@ class _StreamIteratorImpl<T> implements StreamIterator<T> {
 
   Future cancel() {
     StreamSubscription subscription = _subscription;
-    if (subscription == null) return Future._nullFuture;
+    if (subscription == null) return null;
     if (_state == _STATE_MOVING) {
       _Future<bool> hasNext = _futureOrPrefetch as Object /*=_Future<bool>*/;
       _clear();
diff --git a/sdk/lib/async/stream_transformers.dart b/sdk/lib/async/stream_transformers.dart
index 7542c6b88cd..e0982da4260 100644
--- a/sdk/lib/async/stream_transformers.dart
+++ b/sdk/lib/async/stream_transformers.dart
@@ -109,7 +109,7 @@ class _SinkTransformerStreamSubscription<S, T>
     if (_isSubscribed) {
       StreamSubscription subscription = _subscription;
       _subscription = null;
-      return subscription.cancel();
+      subscription.cancel();
     }
     return null;
   }
diff --git a/tests/lib/async/stream_controller_test.dart b/tests/lib/async/stream_controller_test.dart
index 5b019320843..afc7bb53cd9 100644
--- a/tests/lib/async/stream_controller_test.dart
+++ b/tests/lib/async/stream_controller_test.dart
@@ -16,274 +16,237 @@ fail(e) { Expect.fail("Unexepected error: $e"); }
 
 void testMultiController() {
   // Test normal flow.
-  {
-    var c = new StreamController(sync: true);
-    Events expectedEvents = new Events()
-        ..add(42)
-        ..add("dibs")
-        ..error("error!")
-        ..error("error too!")
-        ..close();
-    CaptureEvents actualEvents =
-      new Events.capture(c.stream.asBroadcastStream());
-    expectedEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  var c = new StreamController(sync: true);
+  Events expectedEvents = new Events()
+      ..add(42)
+      ..add("dibs")
+      ..error("error!")
+      ..error("error too!")
+      ..close();
+  CaptureEvents actualEvents = new Events.capture(c.stream.asBroadcastStream());
+  expectedEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test automatic unsubscription on error.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add(42)..error("error");
-    var actualEvents = new Events.capture(c.stream.asBroadcastStream(),
-                                      cancelOnError: true);
-    Events sentEvents =
-        new Events()..add(42)..error("error")..add("Are you there?");
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add(42)..error("error");
+  actualEvents = new Events.capture(c.stream.asBroadcastStream(),
+                                    cancelOnError: true);
+  Events sentEvents =
+      new Events()..add(42)..error("error")..add("Are you there?");
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test manual unsubscription.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add(42)..error("error")..add(37);
-    var actualEvents = new Events.capture(c.stream.asBroadcastStream(),
-                                      cancelOnError: false);
-    expectedEvents.replay(c);
-    actualEvents.subscription.cancel();
-    c.add("Are you there");  // Not sent to actualEvents.
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add(42)..error("error")..add(37);
+  actualEvents = new Events.capture(c.stream.asBroadcastStream(),
+                                    cancelOnError: false);
+  expectedEvents.replay(c);
+  actualEvents.subscription.cancel();
+  c.add("Are you there");  // Not sent to actualEvents.
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test filter.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()
-      ..add("a string")..add("another string")..close();
-    var sentEvents = new Events()
-      ..add("a string")..add(42)..add("another string")..close();
-    var actualEvents = new Events.capture(c.stream
-      .asBroadcastStream()
-      .where((v) => v is String));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()
+    ..add("a string")..add("another string")..close();
+  sentEvents = new Events()
+    ..add("a string")..add(42)..add("another string")..close();
+  actualEvents = new Events.capture(c.stream
+    .asBroadcastStream()
+    .where((v) => v is String));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test map.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add("abab")..error("error")..close();
-    var sentEvents = new Events()..add("ab")..error("error")..close();
-    var actualEvents = new Events.capture(c.stream
-      .asBroadcastStream()
-      .map((v) => "$v$v"));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add("abab")..error("error")..close();
+  sentEvents = new Events()..add("ab")..error("error")..close();
+  actualEvents = new Events.capture(c.stream
+    .asBroadcastStream()
+    .map((v) => "$v$v"));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test handleError.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add("ab")..error("[foo]");
-    var sentEvents = new Events()..add("ab")..error("foo")..add("ab")..close();
-    var actualEvents = new Events.capture(c.stream
-      .asBroadcastStream()
-      .handleError((error) {
-          if (error is String) {
-            // TODO(floitsch): this test originally changed the stacktrace.
-            throw "[${error}]";
-          }
-        }), cancelOnError: true);
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add("ab")..error("[foo]");
+  sentEvents = new Events()..add("ab")..error("foo")..add("ab")..close();
+  actualEvents = new Events.capture(c.stream
+    .asBroadcastStream()
+    .handleError((error) {
+        if (error is String) {
+          // TODO(floitsch): this test originally changed the stacktrace.
+          throw "[${error}]";
+        }
+      }), cancelOnError: true);
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // reduce is tested asynchronously and therefore not in this file.
 
   // Test expand
-  {
-    var c = new StreamController(sync: true);
-    var sentEvents = new Events()..add(3)..add(2)..add(4)..close();
-    var expectedEvents = new Events()..add(1)..add(2)..add(3)
-                                ..add(1)..add(2)
-                                ..add(1)..add(2)..add(3)..add(4)
-                                ..close();
-    var actualEvents =
-        new Events.capture(c.stream.asBroadcastStream().expand((v) {
-      var l = [];
-      for (int i = 0; i < v; i++) l.add(i + 1);
-      return l;
-    }));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  sentEvents = new Events()..add(3)..add(2)..add(4)..close();
+  expectedEvents = new Events()..add(1)..add(2)..add(3)
+                               ..add(1)..add(2)
+                               ..add(1)..add(2)..add(3)..add(4)
+                               ..close();
+  actualEvents = new Events.capture(c.stream.asBroadcastStream().expand((v) {
+    var l = [];
+    for (int i = 0; i < v; i++) l.add(i + 1);
+    return l;
+  }));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test transform.
-  {
-    var c = new StreamController(sync: true);
-    var sentEvents = new Events()..add("a")..error(42)..add("b")..close();
-    var expectedEvents =
-        new Events()..error("a")..add(42)..error("b")..add("foo")..close();
-    var actualEvents =
-        new Events.capture(c.stream.asBroadcastStream().transform(
-        new StreamTransformer.fromHandlers(
-            handleData: (v, s) { s.addError(v); },
-            handleError: (e, st, s) { s.add(e); },
-            handleDone: (s) {
-              s.add("foo");
-              s.close();
-            })));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  sentEvents = new Events()..add("a")..error(42)..add("b")..close();
+  expectedEvents =
+      new Events()..error("a")..add(42)..error("b")..add("foo")..close();
+  actualEvents = new Events.capture(c.stream.asBroadcastStream().transform(
+      new StreamTransformer.fromHandlers(
+          handleData: (v, s) { s.addError(v); },
+          handleError: (e, st, s) { s.add(e); },
+          handleDone: (s) {
+            s.add("foo");
+            s.close();
+          })));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test multiple filters.
-  {
-    var c = new StreamController(sync: true);
-    var sentEvents = new Events()..add(42)
-                            ..add("snugglefluffy")
-                            ..add(7)
-                            ..add("42")
-                            ..error("not FormatException")  // Unsubscribes.
-                            ..close();
-    var expectedEvents = new Events()..add(42)..error("not FormatException");
-    var actualEvents = new Events.capture(
-        c.stream.asBroadcastStream().where((v) => v is String)
-        .map((v) => int.parse(v))
-        .handleError((error) {
-            if (error is! FormatException) throw error;
-          })
-        .where((v) => v > 10),
-        cancelOnError: true);
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  sentEvents = new Events()..add(42)
+                           ..add("snugglefluffy")
+                           ..add(7)
+                           ..add("42")
+                           ..error("not FormatException")  // Unsubscribes.
+                           ..close();
+  expectedEvents = new Events()..add(42)..error("not FormatException");
+  actualEvents = new Events.capture(
+      c.stream.asBroadcastStream().where((v) => v is String)
+       .map((v) => int.parse(v))
+       .handleError((error) {
+          if (error is! FormatException) throw error;
+        })
+       .where((v) => v > 10),
+      cancelOnError: true);
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test subscription changes while firing.
-  {
-    var c = new StreamController(sync: true);
-    var sink = c.sink;
-    var stream = c.stream.asBroadcastStream();
-    var counter = 0;
-    var subscription = stream.listen(null);
-    subscription.onData((data) {
-      counter += data;
-      subscription.cancel();
-      stream.listen((data) {
-        counter += 10 * data;
-      });
-      var subscription2 = stream.listen(null);
-      subscription2.onData((data) {
-        counter += 100 * data;
-        if (data == 4) subscription2.cancel();
-      });
+  c = new StreamController(sync: true);
+  var sink = c.sink;
+  var stream = c.stream.asBroadcastStream();
+  var counter = 0;
+  var subscription = stream.listen(null);
+  subscription.onData((data) {
+    counter += data;
+    subscription.cancel();
+    stream.listen((data) {
+      counter += 10 * data;
     });
-    sink.add(1); // seen by stream 1
-    sink.add(2); // seen by stream 10 and 100
-    sink.add(3); // -"-
-    sink.add(4); // -"-
-    sink.add(5); // seen by stream 10
-    Expect.equals(1 + 20 + 200 + 30 + 300 + 40 + 400 + 50, counter);
-  }
+    var subscription2 = stream.listen(null);
+    subscription2.onData((data) {
+      counter += 100 * data;
+      if (data == 4) subscription2.cancel();
+    });
+  });
+  sink.add(1); // seen by stream 1
+  sink.add(2); // seen by stream 10 and 100
+  sink.add(3); // -"-
+  sink.add(4); // -"-
+  sink.add(5); // seen by stream 10
+  Expect.equals(1 + 20 + 200 + 30 + 300 + 40 + 400 + 50, counter);
 }
 
 testSingleController() {
   // Test normal flow.
-  {
-    var c = new StreamController(sync: true);
-    Events expectedEvents = new Events()
-        ..add(42)
-        ..add("dibs")
-        ..error("error!")
-        ..error("error too!")
-        ..close();
-    CaptureEvents actualEvents = new Events.capture(c.stream);
-    expectedEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  var c = new StreamController(sync: true);
+  Events expectedEvents = new Events()
+      ..add(42)
+      ..add("dibs")
+      ..error("error!")
+      ..error("error too!")
+      ..close();
+  CaptureEvents actualEvents = new Events.capture(c.stream);
+  expectedEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test automatic unsubscription on error.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add(42)..error("error");
-    var actualEvents = new Events.capture(c.stream, cancelOnError: true);
-    Events sentEvents =
-        new Events()..add(42)..error("error")..add("Are you there?");
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add(42)..error("error");
+  actualEvents = new Events.capture(c.stream, cancelOnError: true);
+  Events sentEvents =
+      new Events()..add(42)..error("error")..add("Are you there?");
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test manual unsubscription.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add(42)..error("error")..add(37);
-    var actualEvents = new Events.capture(c.stream, cancelOnError: false);
-    expectedEvents.replay(c);
-    actualEvents.subscription.cancel();
-    c.add("Are you there");  // Not sent to actualEvents.
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add(42)..error("error")..add(37);
+  actualEvents = new Events.capture(c.stream, cancelOnError: false);
+  expectedEvents.replay(c);
+  actualEvents.subscription.cancel();
+  c.add("Are you there");  // Not sent to actualEvents.
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test filter.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()
-      ..add("a string")..add("another string")..close();
-    var sentEvents = new Events()
-      ..add("a string")..add(42)..add("another string")..close();
-    var actualEvents = new Events.capture(c.stream.where((v) => v is String));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()
+    ..add("a string")..add("another string")..close();
+  sentEvents = new Events()
+    ..add("a string")..add(42)..add("another string")..close();
+  actualEvents = new Events.capture(c.stream.where((v) => v is String));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test map.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add("abab")..error("error")..close();
-    var sentEvents = new Events()..add("ab")..error("error")..close();
-    var actualEvents = new Events.capture(c.stream.map((v) => "$v$v"));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add("abab")..error("error")..close();
+  sentEvents = new Events()..add("ab")..error("error")..close();
+  actualEvents = new Events.capture(c.stream.map((v) => "$v$v"));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test handleError.
-  {
-    var c = new StreamController(sync: true);
-    var expectedEvents = new Events()..add("ab")..error("[foo]");
-    var sentEvents = new Events()..add("ab")..error("foo")..add("ab")..close();
-    var actualEvents = new Events.capture(c.stream.handleError((error) {
-          if (error is String) {
-            // TODO(floitsch): this error originally changed the stack trace.
-            throw "[${error}]";
-          }
-        }), cancelOnError: true);
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  expectedEvents = new Events()..add("ab")..error("[foo]");
+  sentEvents = new Events()..add("ab")..error("foo")..add("ab")..close();
+  actualEvents = new Events.capture(c.stream.handleError((error) {
+        if (error is String) {
+          // TODO(floitsch): this error originally changed the stack trace.
+          throw "[${error}]";
+        }
+      }), cancelOnError: true);
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // reduce is tested asynchronously and therefore not in this file.
 
   // Test expand
-  {
-    var c = new StreamController(sync: true);
-    var sentEvents = new Events()..add(3)..add(2)..add(4)..close();
-    var expectedEvents = new Events()..add(1)..add(2)..add(3)
-                                ..add(1)..add(2)
-                                ..add(1)..add(2)..add(3)..add(4)
-                                ..close();
-    var actualEvents = new Events.capture(c.stream.expand((v) {
-      var l = [];
-      for (int i = 0; i < v; i++) l.add(i + 1);
-      return l;
-    }));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  sentEvents = new Events()..add(3)..add(2)..add(4)..close();
+  expectedEvents = new Events()..add(1)..add(2)..add(3)
+                               ..add(1)..add(2)
+                               ..add(1)..add(2)..add(3)..add(4)
+                               ..close();
+  actualEvents = new Events.capture(c.stream.expand((v) {
+    var l = [];
+    for (int i = 0; i < v; i++) l.add(i + 1);
+    return l;
+  }));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // test contains.
   {
-    var c = new StreamController(sync: true);
+    c = new StreamController(sync: true);
     // Error after match is not important.
-    var sentEvents = new Events()..add("a")..add("x")..error("FAIL")..close();
+    sentEvents = new Events()..add("a")..add("x")..error("FAIL")..close();
     Future<bool> contains = c.stream.contains("x");
     contains.then((var c) {
       Expect.isTrue(c);
@@ -292,9 +255,9 @@ testSingleController() {
   }
 
   {
-    var c = new StreamController(sync: true);
+    c = new StreamController(sync: true);
     // Not matching is ok.
-    var sentEvents = new Events()..add("a")..add("x")..add("b")..close();
+    sentEvents = new Events()..add("a")..add("x")..add("b")..close();
     Future<bool> contains = c.stream.contains("y");
     contains.then((var c) {
       Expect.isFalse(c);
@@ -303,9 +266,9 @@ testSingleController() {
   }
 
   {
-    var c = new StreamController(sync: true);
+    c = new StreamController(sync: true);
     // Error before match makes future err.
-    var sentEvents = new Events()..add("a")..error("FAIL")..add("b")..close();
+    sentEvents = new Events()..add("a")..error("FAIL")..add("b")..close();
     Future<bool> contains = c.stream.contains("b");
     contains.then((var c) {
       Expect.fail("no value expected");
@@ -316,57 +279,51 @@ testSingleController() {
   }
 
   // Test transform.
-  {
-    var c = new StreamController(sync: true);
-    var sentEvents = new Events()..add("a")..error(42)..add("b")..close();
-    var expectedEvents =
-        new Events()..error("a")..add(42)..error("b")..add("foo")..close();
-    var actualEvents = new Events.capture(c.stream.transform(
-        new StreamTransformer.fromHandlers(
-            handleData: (v, s) { s.addError(v); },
-            handleError: (e, st, s) { s.add(e); },
-            handleDone: (s) {
-              s.add("foo");
-              s.close();
-            })));
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  sentEvents = new Events()..add("a")..error(42)..add("b")..close();
+  expectedEvents =
+      new Events()..error("a")..add(42)..error("b")..add("foo")..close();
+  actualEvents = new Events.capture(c.stream.transform(
+      new StreamTransformer.fromHandlers(
+          handleData: (v, s) { s.addError(v); },
+          handleError: (e, st, s) { s.add(e); },
+          handleDone: (s) {
+            s.add("foo");
+            s.close();
+          })));
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test multiple filters.
-  {
-    var c = new StreamController(sync: true);
-    var sentEvents = new Events()..add(42)
-                            ..add("snugglefluffy")
-                            ..add(7)
-                            ..add("42")
-                            ..error("not FormatException")  // Unsubscribes.
-                            ..close();
-    var expectedEvents = new Events()..add(42)..error("not FormatException");
-    var actualEvents = new Events.capture(
-        c.stream.where((v) => v is String)
-        .map((v) => int.parse(v))
-        .handleError((error) {
-            if (error is! FormatException) throw error;
-          })
-        .where((v) => v > 10),
-        cancelOnError: true);
-    sentEvents.replay(c);
-    Expect.listEquals(expectedEvents.events, actualEvents.events);
-  }
+  c = new StreamController(sync: true);
+  sentEvents = new Events()..add(42)
+                           ..add("snugglefluffy")
+                           ..add(7)
+                           ..add("42")
+                           ..error("not FormatException")  // Unsubscribes.
+                           ..close();
+  expectedEvents = new Events()..add(42)..error("not FormatException");
+  actualEvents = new Events.capture(
+      c.stream.where((v) => v is String)
+       .map((v) => int.parse(v))
+       .handleError((error) {
+          if (error is! FormatException) throw error;
+        })
+       .where((v) => v > 10),
+      cancelOnError: true);
+  sentEvents.replay(c);
+  Expect.listEquals(expectedEvents.events, actualEvents.events);
 
   // Test that only one subscription is allowed.
-  {
-    var c = new StreamController(sync: true);
-    var sink = c.sink;
-    var stream = c.stream;
-    var counter = 0;
-    var subscription = stream.listen((data) { counter += data; });
-    Expect.throws(() => stream.listen(null), (e) => e is StateError);
-    sink.add(1);
-    Expect.equals(1, counter);
-    c.close();
-  }
+  c = new StreamController(sync: true);
+  var sink = c.sink;
+  var stream = c.stream;
+  var counter = 0;
+  var subscription = stream.listen((data) { counter += data; });
+  Expect.throws(() => stream.listen(null), (e) => e is StateError);
+  sink.add(1);
+  Expect.equals(1, counter);
+  c.close();
 }
 
 testExtraMethods() {
diff --git a/tests/lib/async/stream_periodic_test.dart b/tests/lib/async/stream_periodic_test.dart
index f755d76ef41..b333966065b 100644
--- a/tests/lib/async/stream_periodic_test.dart
+++ b/tests/lib/async/stream_periodic_test.dart
@@ -16,10 +16,7 @@ main() {
     subscription = stream.listen(expectAsync((data) {
       expect(data, isNull);
       receivedCount++;
-      if (receivedCount == 5) {
-        var future = subscription.cancel();
-        expect(future, completes);
-      }
+      if (receivedCount == 5) subscription.cancel();
     }, count: 5));
   });
 }
diff --git a/tests/lib/async/stream_subscription_as_future_test.dart b/tests/lib/async/stream_subscription_as_future_test.dart
index 841298b1990..ac1293b0297 100644
--- a/tests/lib/async/stream_subscription_as_future_test.dart
+++ b/tests/lib/async/stream_subscription_as_future_test.dart
@@ -10,7 +10,7 @@ import 'dart:async';
 import 'package:unittest/unittest.dart';
 
 main() {
-  test("subscription.asFuture success", () {
+  test("subscription.asStream success", () {
     Stream stream = new Stream.fromIterable([1, 2, 3]);
     var output = [];
     var subscription = stream.listen((x) { output.add(x); });
@@ -19,7 +19,7 @@ main() {
     }));
   });
 
-  test("subscription.asFuture success2", () {
+  test("subscription.asStream success2", () {
     StreamController controller = new StreamController(sync: true);
     [1, 2, 3].forEach(controller.add);
     controller.close();
@@ -31,7 +31,7 @@ main() {
     }));
   });
 
-  test("subscription.asFuture success 3", () {
+  test("subscription.asStream success 3", () {
     Stream stream = new Stream.fromIterable([1, 2, 3]).map((x) => x);
     var output = [];
     var subscription = stream.listen((x) { output.add(x); });
@@ -40,7 +40,7 @@ main() {
     }));
   });
 
-  test("subscription.asFuture different type", () {
+  test("subscription.asStream different type", () {
     Stream stream = new Stream<int>.fromIterable([1, 2, 3]);
     var asyncCallback = expectAsync(() => {});
     var output = [];
@@ -52,7 +52,7 @@ main() {
     });
   });
 
-  test("subscription.asFuture failure", () {
+  test("subscription.asStream failure", () {
     StreamController controller = new StreamController(sync: true);
     [1, 2, 3].forEach(controller.add);
     controller.addError("foo");
@@ -65,7 +65,7 @@ main() {
     }));
   });
 
-  test("subscription.asFuture failure2", () {
+  test("subscription.asStream failure2", () {
     Stream stream = new Stream.fromIterable([1, 2, 3, 4])
       .map((x) {
         if (x == 4) throw "foo";
@@ -77,50 +77,4 @@ main() {
       Expect.equals(error, "foo");
     }));
   });
-
-  test("subscription.asFuture delayed cancel", () {
-    var completer = new Completer();
-    var controller =
-        new StreamController(onCancel: () => completer.future, sync: true);
-    [1, 2, 3].forEach(controller.add);
-    controller.addError("foo");
-    controller.close();
-    Stream stream = controller.stream;
-    var output = [];
-    var subscription = stream.listen((x) { output.add(x); });
-    bool catchErrorHasRun = false;
-    subscription.asFuture(output).catchError(expectAsync((error) {
-      Expect.equals(error, "foo");
-      catchErrorHasRun = true;
-    }));
-    Timer.run(expectAsync(() {
-      Expect.isFalse(catchErrorHasRun);
-      completer.complete();
-    }));
-  });
-
-  test("subscription.asFuture failure in cancel", () {
-    runZoned(() {
-      var completer = new Completer();
-      var controller =
-          new StreamController(onCancel: () => completer.future, sync: true);
-      [1, 2, 3].forEach(controller.add);
-      controller.addError("foo");
-      controller.close();
-      Stream stream = controller.stream;
-      var output = [];
-      var subscription = stream.listen((x) { output.add(x); });
-      bool catchErrorHasRun = false;
-      subscription.asFuture(output).catchError(expectAsync((error) {
-        Expect.equals(error, "foo");
-        catchErrorHasRun = true;
-      }));
-      Timer.run(expectAsync(() {
-        Expect.isFalse(catchErrorHasRun);
-        completer.completeError(499);
-      }));
-    }, onError: expectAsync((e) {
-      Expect.equals(499, e);
-    }));
-  });
 }
diff --git a/tests/lib/async/stream_subscription_cancel_test.dart b/tests/lib/async/stream_subscription_cancel_test.dart
index 48649b2717d..d6c6987545f 100644
--- a/tests/lib/async/stream_subscription_cancel_test.dart
+++ b/tests/lib/async/stream_subscription_cancel_test.dart
@@ -27,22 +27,17 @@ void main() {
   test('subscription.cancel after close', () {
     var completer = new Completer();
     StreamController controller = new StreamController(
-        onCancel: () {
-          completer.complete();
-          return completer.future;
-        });
+        onCancel: completer.complete);
 
     controller.close();
 
-    var completer2 = new Completer();
     var sub;
     void onDone() {
-      sub.cancel().then(completer2.complete);
+      expect(sub.cancel(), isNull);
     }
 
     sub = controller.stream.listen(null, onDone: onDone);
     expect(completer.future, completes);
-    expect(completer2.future, completes);
   });
 
   test('subscription.cancel after error', () {
@@ -140,183 +135,4 @@ void main() {
       .cancel();
     expect(doneCompleter.future, completion(equals(true)));
   });
-
-  test('subscription.cancel through map', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.map((x) => x).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through asyncMap', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.asyncMap((x) => x).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through asyncExpand', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.asyncExpand((x) => x).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through handleError', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.handleError((x) => x).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through skip', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.skip(1).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through take', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.take(1).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through skipWhile', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.skipWhile((x) => true).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through takeWhile', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.takeWhile((x) => true).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through timeOut', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var duration = const Duration(hours: 5);
-    var future = controller.stream.timeout(duration).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through transform', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var transformer =
-        new StreamTransformer.fromHandlers(handleData: (x, y) {});
-    var future = controller.stream.transform(transformer).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
-
-  test('subscription.cancel through where', () {
-    var completer = new Completer();
-    StreamController controller = new StreamController(
-        onCancel: () => completer.future);
-
-    bool done = false;
-    var future = controller.stream.where((x) => true).listen(null).cancel();
-
-    expect(future.then((_) => done = true), completion(equals(true)));
-
-    Timer.run(() {
-      expect(done, isFalse);
-      completer.complete();
-    });
-  });
 }
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index 4b30359c2b1..469b3b3023d 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -166,7 +166,6 @@ async/stream_asyncexpand_test: RuntimeError # Timer interface not supported: Iss
 async/stream_asyncmap_test: RuntimeError # Timer interface not supported: Issue 7728.
 async/stream_transformation_broadcast_test: RuntimeError # Timer interface not supported: Issue 7728.
 async/stream_controller_test: Fail # Timer interface not supported: Issue 7728.
-async/stream_subscription_cancel_test: Fail # Timer interface not supported: Issue 7728.
 async/future_constructor2_test: Fail # Timer interface not supported: Issue 7728.
 mirrors/mirrors_reader_test: Skip # Running in v8 suffices. Issue 16589 - RuntimeError.  Issue 22130 - Crash (out of memory).