Fix sound not playing in Dartium checked mode.

sdk/lib/web_audio/dartium/web_audio_dartium.dart

 /**
  * High-fidelity audio programming in the browser.
  */
 library dart.dom.web_audio;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_internal';
 import 'dart:html';
 import 'dart:html_common';
@@ skipping 528 matching lines @@
   @DocsEditable()
   @Experimental() // untriaged
   StereoPannerNode createStereoPanner() =>
       _blink.BlinkAudioContext.instance.createStereoPanner_Callback_0_(this);
 
   @DomName('AudioContext.createWaveShaper')
   @DocsEditable()
   WaveShaperNode createWaveShaper() =>
       _blink.BlinkAudioContext.instance.createWaveShaper_Callback_0_(this);
 
-  Future _decodeAudioData(ByteBuffer audioData,
-      [AudioBufferCallback successCallback,
-      AudioBufferCallback errorCallback]) {
-    if (errorCallback != null) {
-      return _blink.BlinkAudioContext.instance.decodeAudioData_Callback_3_(
-          this, audioData, successCallback, errorCallback);
-    }
-    if (successCallback != null) {
-      return _blink.BlinkAudioContext.instance
-          .decodeAudioData_Callback_2_(this, audioData, successCallback);
-    }
-    return _blink.BlinkAudioContext.instance
-        .decodeAudioData_Callback_1_(this, audioData);
-  }
-
   @DomName('AudioContext.resume')
   @DocsEditable()
   @Experimental() // untriaged
   Future resume() => convertNativePromiseToDartFuture(
       _blink.BlinkAudioContext.instance.resume_Callback_0_(this));
 
   @DomName('AudioContext.suspend')
   @DocsEditable()
   @Experimental() // untriaged
   Future suspend() => convertNativePromiseToDartFuture(
       _blink.BlinkAudioContext.instance.suspend_Callback_0_(this));
 
   @DomName('AudioContext.decodeAudioData')
-  Future<AudioBuffer> decodeAudioData(ByteBuffer audioData) {
-    var completer = new Completer<AudioBuffer>();
-    _decodeAudioData(audioData, (value) {
-      completer.complete(value);
-    }, (error) {
-      if (error == null) {
-        completer.completeError('');
-      } else {
-        completer.completeError(error);
-      }
-    });
-    return completer.future;
+  Future<AudioBuffer> decodeAudioData(ByteBuffer audioData,
+      [AudioBufferCallback successCallback,
+      AudioBufferCallback errorCallback]) {
+    if (errorCallback != null) {
+      return convertNativePromiseToDartFuture(_blink.BlinkAudioContext.instance
+          .decodeAudioData_Callback_3_(
+              this, audioData, successCallback, errorCallback));
+    }
+    if (successCallback != null) {
+      return convertNativePromiseToDartFuture(_blink.BlinkAudioContext.instance
+          .decodeAudioData_Callback_2_(this, audioData, successCallback));
+    }
+    return convertNativePromiseToDartFuture(_blink.BlinkAudioContext.instance
+        .decodeAudioData_Callback_1_(this, audioData));
   }
 }
 // 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.
 
 // WARNING: Do not edit - generated code.
 
 @DocsEditable()
 @DomName('AudioDestinationNode')
@@ skipping 1145 matching lines @@
   @DomName('WaveShaperNode.oversample')
   @DocsEditable()
   String get oversample =>
       _blink.BlinkWaveShaperNode.instance.oversample_Getter_(this);
 
   @DomName('WaveShaperNode.oversample')
   @DocsEditable()
   set oversample(String value) =>
       _blink.BlinkWaveShaperNode.instance.oversample_Setter_(this, value);
 }