Reapply "Active stream subscriptions".

tests/lib/async/stream_controller_async_test.dart

Index: tests/lib/async/stream_controller_async_test.dart
diff --git a/tests/lib/async/stream_controller_async_test.dart b/tests/lib/async/stream_controller_async_test.dart
index e2aab21d6da40b916a4f6d232e33b0ff1c487c7d..53be91005be249e8497bcff6447cc80b59971768 100644
--- a/tests/lib/async/stream_controller_async_test.dart
+++ b/tests/lib/async/stream_controller_async_test.dart
@@ -53,28 +53,6 @@ testSingleController() {
     c.add(42);
   });
 
-  test("Single-subscription StreamController subscription changes", () {
-    StreamController c = new StreamController();
-    EventSink 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.cancel();
-      stream.listen((data) {
-        counter += data * 10;
-      },
-      onDone: expectAsync0(() {
-        Expect.equals(1 + 20, counter);
-      }));
-    });
-    sink.add(1);
-    sink.add(2);
-    sink.close();
-  });
-
   test("Single-subscription StreamController events are buffered when"
        " there is no subscriber",
        () {
@@ -93,33 +71,6 @@ testSingleController() {
         Expect.equals(3, counter);
       }));
   });
-
-  // Test subscription changes while firing.
-  test("Single-subscription StreamController subscription changes while firing",
-       () {
-    StreamController c = new StreamController();
-    EventSink sink = c.sink;
-    Stream stream = c.stream;
-    int counter = 0;
-    var subscription = stream.listen(null);
-    subscription.onData(expectAsync1((data) {
-      counter += data;
-      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
-    sink.add(3); // -"-
-    sink.add(4); // -"-
-    sink.add(5); // seen by stream 10
-    sink.close();
-  });
 }
 
 testExtraMethods() {
@@ -478,10 +429,66 @@ testRethrow() {
   testFuture("drain", (s, act) => s.drain().then(act));
 }
 
+void testMultiplex() {
+  test("multiplex-basic", () {
+    StreamController<int> c = new StreamController.multiplex(
+      onListen: expectAsync0(() {}),
+      onCancel: expectAsync0(() {})
+    );
+    Stream<int> s = c.stream;
+    s.listen(expectAsync1((x) { expect(x, equals(42)); }));
+    c.add(42);
+    c.close();
+  });
+
+  test("multiplex-listen-twice", () {
+    StreamController<int> c = new StreamController.multiplex(
+      onListen: expectAsync0(() {}),
+      onCancel: expectAsync0(() {})
+    );
+    c.stream.listen(expectAsync1((x) { expect(x, equals(42)); }, count: 2));
+    c.add(42);
+    c.stream.listen(expectAsync1((x) { expect(x, equals(42)); }));
+    c.add(42);
+    c.close();
+  });
+
+  test("multiplex-listen-twice-non-overlap", () {
+    StreamController<int> c = new StreamController.multiplex(
+      onListen: expectAsync0(() {}, count: 2),
+      onCancel: expectAsync0(() {}, count: 2)
+    );
+    var sub = c.stream.listen(expectAsync1((x) { expect(x, equals(42)); }));
+    c.add(42);
+    sub.cancel();
+    c.stream.listen(expectAsync1((x) { expect(x, equals(42)); }));
+    c.add(42);
+    c.close();
+  });
+
+  test("multiplex-individual-pause", () {
+    StreamController<int> c = new StreamController.multiplex(
+      onListen: expectAsync0(() {}),
+      onCancel: expectAsync0(() {})
+    );
+    var sub1 = c.stream.listen(expectAsync1((x) { expect(x, equals(42)); }));
+    var sub2 = c.stream.listen(expectAsync1((x) { expect(x, equals(42)); },
+                                            count: 3));
+    c.add(42);
+    sub1.pause();
+    c.add(42);
+    sub1.cancel();
+    var sub3 = c.stream.listen(expectAsync1((x) { expect(x, equals(42)); }));
+    c.add(42);
+    c.close();
+  });
+}
+
 main() {
   testController();
   testSingleController();
   testExtraMethods();
   testPause();
   testRethrow();
+  testMultiplex();
 }