Don't use => on void functions.

sdk/lib/web_audio/dart2js/web_audio_dart2js.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 458 matching lines @@
   @DocsEditable()
   final int numberOfInputs;
 
   @DomName('AudioNode.numberOfOutputs')
   @DocsEditable()
   final int numberOfOutputs;
 
   @JSName('connect')
   @DomName('AudioNode.connect')
   @DocsEditable()
   void _connect(destination, [int output, int input]) native;

[floitsch, 2016/07/08 18:02:32]

Fwiw: the "_connect" return type is probably not correct anymore, since the
value here is not 'null'.

Probably should be changed here to the correct type.
We are just lucky that dart2js doesn't check the return type for native
functions.

[sra1, 2016/07/08 18:12:03]

The return type of native functions is assumed to be correct.

Change this to something that is correct (e.g. dynamic), then the => would have
been a warning.

[floitsch, 2016/07/11 12:20:04]

I don't know how to change this.
This part seems to be generated. I'm guessing it is extracted from the DOM
specification which has changed.
This probably was correct for older versions of Chrome, but isn't anymore.

 
   @DomName('AudioNode.disconnect')
   @DocsEditable()
   void disconnect([destination_OR_output, int output, int input]) native;
 
   @DomName('AudioNode.connect')
-  void connectNode(AudioNode destination, [int output = 0, int input = 0]) =>
-      _connect(destination, output, input);
+  void connectNode(AudioNode destination, [int output = 0, int input = 0]) {
+    _connect(destination, output, input);
+  }
 
   @DomName('AudioNode.connect')
-  void connectParam(AudioParam destination, [int output = 0]) =>
-      _connect(destination, output);
+  void connectParam(AudioParam destination, [int output = 0]) {
+    _connect(destination, output);
+  }
 }
 // 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.
 
 
 @DocsEditable()
 @DomName('AudioParam')
 // https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#AudioParam
 @Experimental()
@@ skipping 543 matching lines @@
   factory WaveShaperNode._() { throw new UnsupportedError("Not supported"); }
 
   @DomName('WaveShaperNode.curve')
   @DocsEditable()
   Float32List curve;
 
   @DomName('WaveShaperNode.oversample')
   @DocsEditable()
   String oversample;
 }