Refactor Future constructors.

tests/lib/async/slow_consumer_test.dart

 // Copyright (c) 2012, 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.
 
 // VMOptions=--old_gen_heap_size=64
 
 library slow_consumer_test;
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:isolate';
 
 const int KB = 1024;
 const int MB = KB * KB;
 const int GB = KB * KB * KB;
 
 class SlowConsumer extends StreamConsumer {
-  var current = new Future.immediate(0);
+  var current = new Future.value(0);
   final int bytesPerSecond;
   int finalCount;
 
   SlowConsumer(int this.bytesPerSecond);
 
   Future consume(Stream stream) {
     return addStream(stream).then((_) => close());
   }
 
   Future addStream(Stream stream) {
@@ skipping 19 matching lines @@
         done = true;
         current.then((count) {
           finalCount = count;
           completer.complete(count);
         });
       });
     return completer.future;
   }
 
   Future close() {
-    return new Future.immediate(finalCount);
+    return new Future.value(finalCount);
   }
 }
 
 class DataProvider {
   final int chunkSize;
   final int bytesPerSecond;
   int sentCount = 0;
   int targetCount;
   StreamController controller;
   Timer pendingSend;
@@ skipping 48 matching lines @@
   // file). If the consumer doesn't pause the data-provider it will run out of
   // heap-space.
 
   new DataProvider(800 * MB, 100 * MB, 1 * MB).stream
     .pipe(new SlowConsumer(200 * MB))
     .then((count) {
       port.close();
       Expect.equals(100 * MB, count);
     });
 }