Implement everything in test Future-class to avoid analyzer warnings.

tests/lib/async/future_test.dart

Index: tests/lib/async/future_test.dart
diff --git a/tests/lib/async/future_test.dart b/tests/lib/async/future_test.dart
index 6699a6957a8c51e17f4deecaf4e31818f5073699..52185f2ae8044981b6624bb2b8f9a4ecf246b3c5 100644
--- a/tests/lib/async/future_test.dart
+++ b/tests/lib/async/future_test.dart
@@ -1135,8 +1135,14 @@ class UglyFuture implements Future<dynamic> {
     c.complete(new Future.microtask(() => action(_result)));
     return c.future;
   }
-  Future catchError(onError, {test}) {}  // Never an error.
+  Future catchError(onError, {test}) => this;  // Never an error.
   Future whenComplete(action()) {
     return new Future.microtask(action).then((_) => this);
   }
+  Stream asStream() {
+    return (new StreamController()..add(_result)..close()).stream;
+  }
+  Future timeout(Duration duration, {onTimeout()}) {
+    return this;
+  }
 }