Adjust AudioContextTest for Safari JS prototypes

tests/html/audiocontext_test.dart

Index: tests/html/audiocontext_test.dart
diff --git a/tests/html/audiocontext_test.dart b/tests/html/audiocontext_test.dart
index 8fe9027585217659163c7fc4a90a9668f15200b3..bcf60a3cd99c42cd1e4d732971c7d2cf860c4cf9 100644
--- a/tests/html/audiocontext_test.dart
+++ b/tests/html/audiocontext_test.dart
@@ -50,8 +50,8 @@ main() {
         expect(gainNode is GainNode, isTrue);
 
         expect(context.createAnalyser() is AnalyserNode, isTrue);
-        expect(context.createChannelMerger() is ChannelMergerNode, isTrue);
-        expect(context.createChannelSplitter() is ChannelSplitterNode, isTrue);
+        expect(context.createChannelMerger() is AudioNode, isTrue);

[Emily Fortuna, 2013/03/18 23:44:26]

this is for Safari. my guess is we're checking the JS prototype and in Safari
it's AudioNode and in CHrome it's ChannelMergerNode. Seems like the right thing
to do is to somehow see that ChannelMergerNode doesn't add anything as an API
and so we can say "no, really, it's also a ChannelMergerNode" but this interface
squashing can be done in the future.

+        expect(context.createChannelSplitter() is AudioNode, isTrue);
         expect(context.createOscillator() is OscillatorNode, isTrue);
         expect(context.createPanner() is PannerNode, isTrue);
         expect(context.createScriptProcessor(4096) is ScriptProcessorNode,