Fix Dart 1.17 strong-mode warnings.

test/stream_zip_test.dart

 // Copyright (c) 2013, 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 "package:async/async.dart";
 import "package:test/test.dart";
 
 /// Create an error with the same values as [base], except that it throwsA
@@ skipping 18 matching lines @@
     }
   });
   return controller.stream;
 }
 
 /// Counter used to give varying delays for streams.
 int ctr = 0;
 
 main() {
   // Test that zipping [streams] gives the results iterated by [expectedData].
-  testZip(Iterable streams, Iterable expectedData) {
+  testZip(Iterable<Stream> streams, Iterable expectedData) {
     List data = [];
     Stream zip = new StreamZip(streams);
     zip.listen(data.add, onDone: expectAsync(() {
       expect(data, equals(expectedData));
     }));
   }
 
   test("Basic", () {
     testZip([mks([1, 2, 3]), mks([4, 5, 6]), mks([7, 8, 9])],
             [[1, 4, 7], [2, 5, 8], [3, 6, 9]]);
@@ skipping 177 matching lines @@
       } else if (ctr == 2) {
         sub.pause();
         new Future.delayed(const Duration(milliseconds: 25)).then((_) {
           sub.resume();
         });
       }
       ctr++;
     }, count: 4));
   });
 }