Adapt streams for additional stackTrace argument.

tests/lib/async/stack_trace20_test.dart

Index: tests/lib/async/stack_trace20_test.dart
diff --git a/tests/lib/async/stack_trace14_test.dart b/tests/lib/async/stack_trace20_test.dart
similarity index 67%
copy from tests/lib/async/stack_trace14_test.dart
copy to tests/lib/async/stack_trace20_test.dart
index 1a75c88c56d751b576bde8a9ee2adc815921c7dc..aaec9982b0e85947d03d53759706d16802f16fd4 100644
--- a/tests/lib/async/stack_trace14_test.dart
+++ b/tests/lib/async/stack_trace20_test.dart
@@ -16,12 +16,18 @@ StackTrace captureStackTrace() {
 
 main() {
   StackTrace trace = captureStackTrace();
+  var controller;
+  controller = new StreamController(onListen: () {
+    controller.addError("error", trace);
+    controller.close();
+  });
   asyncStart();
-  var f = new Future(() => 499);
-  f.then((_) => new Future.error("e", trace))
-    .then((_) { throw "Unreachable"; },
+  controller.stream
+    .listen(null)
+    .asFuture()
+    .then((_) { throw "should never be reached"; },
       onError: (e, st) {
-        Expect.equals("e", e);
+        Expect.equals("error", e);
         Expect.identical(trace, st);
         asyncEnd();
       });