Fix all strong-mode warnings.

test/transformer/mock_aggregate.dart

 // Copyright (c) 2014, 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.
 
 library barback.test.transformer.mock_aggregate;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:barback/src/utils.dart';
@@ skipping 135 matching lines @@
   void resumePrimaryInputs() {
     schedule(() {
       _primaryInputs.complete();
       _primaryInputs = null;
     }, "resume primaryInputs for $this");
   }
 
   /// Like [AggregateTransform.getInput], but respects [pauseGetInput].
   ///
   /// This is intended for use by subclasses of [MockAggregateTransformer].
-  Future<Asset> getInput(AggregateTransform transform, AssetId id) {
-    return newFuture(() {
-      if (_getInput.containsKey(id)) return _getInput[id].future;
-    }).then((_) => transform.getInput(id));
+  Future<Asset> getInput(AggregateTransform transform, AssetId id) async {
+    if (_getInput.containsKey(id)) await _getInput[id].future;
+    return await transform.getInput(id);
   }
 
   /// Like [AggregateTransform.primaryInputs], but respects
   /// [pausePrimaryInputs].
   ///
   /// This is intended for use by subclasses of [MockAggregateTransformer].
   Stream<Asset> getPrimaryInputs(AggregateTransform transform) {
     return futureStream(newFuture(() {
       if (_primaryInputs != null) return _primaryInputs.future;
     }).then((_) => transform.primaryInputs));
   }
 
-  Future<String> classifyPrimary(AssetId id) {
-    return newFuture(() => doClassifyPrimary(id)).then((result) {
-      return newFuture(() {
-        if (_classifyPrimary.containsKey(id)) {
-          return _classifyPrimary[id].future;
-        }
-      }).then((_) => result);
-    });
+  Future<String> classifyPrimary(AssetId id) async {
+    var result = await doClassifyPrimary(id);
+    if (_classifyPrimary.containsKey(id)) await _classifyPrimary[id].future;
+    return result;
   }
 
   Future apply(AggregateTransform transform) {
     _numRuns++;
     if (_runningTransforms == 0) _started.complete();
     _runningTransforms++;
     return newFuture(() => doApply(transform)).then((_) {
       if (_apply != null) return _apply.future;
     }).whenComplete(() {
       for (var id in consumePrimaries) {
         transform.consumePrimary(new AssetId.parse(id));
       }
       _runningTransforms--;
       if (_runningTransforms == 0) _started = new Completer();
     });
   }
 
   /// The wrapped version of [classifyPrimary] for subclasses to override.
   ///
   /// This may return a `Future<String>` or, if it's entirely synchronous, a
   /// `String`.
   doClassifyPrimary(AssetId id);
 
   /// The wrapped version of [doApply] for subclasses to override.
   ///
   /// If this does asynchronous work, it should return a [Future] that completes
   /// once it's finished.
   doApply(AggregateTransform transform);
 }