Modify blink type map to finalize lazily

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 d0e18f876d76ed6dbc3e11e45858f3da8dc81218..8cdf0ea22c33601bf5821770c974c44d329de319 100644
--- a/sdk/lib/web_audio/dartium/web_audio_dartium.dart
+++ b/sdk/lib/web_audio/dartium/web_audio_dartium.dart
@@ -15,34 +15,34 @@ import 'dart:_blink' as _blink;
 
 
 // FIXME: Can we make this private?
-const web_audioBlinkMap = const {
-  'AnalyserNode': AnalyserNode,
-  'AudioBuffer': AudioBuffer,
-  'AudioBufferSourceNode': AudioBufferSourceNode,
-  'AudioContext': AudioContext,
-  'AudioDestinationNode': AudioDestinationNode,
-  'AudioListener': AudioListener,
-  'AudioNode': AudioNode,
-  'AudioParam': AudioParam,
-  'AudioProcessingEvent': AudioProcessingEvent,
-  'AudioSourceNode': AudioSourceNode,
-  'BiquadFilterNode': BiquadFilterNode,
-  'ChannelMergerNode': ChannelMergerNode,
-  'ChannelSplitterNode': ChannelSplitterNode,
-  'ConvolverNode': ConvolverNode,
-  'DelayNode': DelayNode,
-  'DynamicsCompressorNode': DynamicsCompressorNode,
-  'GainNode': GainNode,
-  'MediaElementAudioSourceNode': MediaElementAudioSourceNode,
-  'MediaStreamAudioDestinationNode': MediaStreamAudioDestinationNode,
-  'MediaStreamAudioSourceNode': MediaStreamAudioSourceNode,
-  'OfflineAudioCompletionEvent': OfflineAudioCompletionEvent,
-  'OfflineAudioContext': OfflineAudioContext,
-  'OscillatorNode': OscillatorNode,
-  'PannerNode': PannerNode,
-  'PeriodicWave': PeriodicWave,
-  'ScriptProcessorNode': ScriptProcessorNode,
-  'WaveShaperNode': WaveShaperNode,
+final web_audioBlinkMap = {
+  'AnalyserNode': () => AnalyserNode,
+  'AudioBuffer': () => AudioBuffer,
+  'AudioBufferSourceNode': () => AudioBufferSourceNode,
+  'AudioContext': () => AudioContext,
+  'AudioDestinationNode': () => AudioDestinationNode,
+  'AudioListener': () => AudioListener,
+  'AudioNode': () => AudioNode,
+  'AudioParam': () => AudioParam,
+  'AudioProcessingEvent': () => AudioProcessingEvent,
+  'AudioSourceNode': () => AudioSourceNode,
+  'BiquadFilterNode': () => BiquadFilterNode,
+  'ChannelMergerNode': () => ChannelMergerNode,
+  'ChannelSplitterNode': () => ChannelSplitterNode,
+  'ConvolverNode': () => ConvolverNode,
+  'DelayNode': () => DelayNode,
+  'DynamicsCompressorNode': () => DynamicsCompressorNode,
+  'GainNode': () => GainNode,
+  'MediaElementAudioSourceNode': () => MediaElementAudioSourceNode,
+  'MediaStreamAudioDestinationNode': () => MediaStreamAudioDestinationNode,
+  'MediaStreamAudioSourceNode': () => MediaStreamAudioSourceNode,
+  'OfflineAudioCompletionEvent': () => OfflineAudioCompletionEvent,
+  'OfflineAudioContext': () => OfflineAudioContext,
+  'OscillatorNode': () => OscillatorNode,
+  'PannerNode': () => PannerNode,
+  'PeriodicWave': () => PeriodicWave,
+  'ScriptProcessorNode': () => ScriptProcessorNode,
+  'WaveShaperNode': () => WaveShaperNode,
 
 };
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file