Remove some usages of IterableMixinWorkaround from HTML library.

sdk/lib/web_audio/dartium/web_audio_dartium.dart

Index: sdk/lib/web_audio/dartium/web_audio_dartium.dart
diff --git a/sdk/lib/web_audio/dartium/web_audio_dartium.dart b/sdk/lib/web_audio/dartium/web_audio_dartium.dart
index 4b410d1d43e5e10ee82b1ccb54890ff2f20dc74f..99c09b82150fef3bc2508e0f6603c4be146fe666 100644
--- a/sdk/lib/web_audio/dartium/web_audio_dartium.dart
+++ b/sdk/lib/web_audio/dartium/web_audio_dartium.dart
@@ -231,10 +231,6 @@ class AudioContext extends EventTarget {
   @DomName('AudioContext.completeEvent')
   @DocsEditable
   static const EventStreamProvider<Event> completeEvent = const EventStreamProvider<Event>('complete');
-  factory AudioContext() => _create();
-
-  @DocsEditable
-  static AudioContext _create() native "AudioContext_constructorCallback";
 
   /// Checks if this type is supported on the current platform.
   static bool get supported => true;
@@ -1117,10 +1113,6 @@ class ScriptProcessorNode extends AudioNode {
   @DocsEditable
   int get bufferSize native "ScriptProcessorNode_bufferSize_Getter";
 
-  @DomName('ScriptProcessorNode._setEventListener')
-  @DocsEditable
-  void _setEventListener(EventListener eventListener) native "ScriptProcessorNode__setEventListener_Callback";
-
 }
 // 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