Web MIDI: refine MIDIAccessor and WebMIDIAccessor APIs

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index 5f974adb329fcc7d98a246383baedced0ea5bf3f..226f4f9eacedba5647b31dd1ab8032dd519e5166 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -153,12 +153,14 @@ public:
     virtual WebAudioDevice* createAudioDevice(size_t bufferSize, unsigned numberOfChannels, double sampleRate, WebAudioDevice::RenderCallback*) { return 0; }
     virtual WebAudioDevice* createAudioDevice(size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfChannels, double sampleRate, WebAudioDevice::RenderCallback*) { return 0; }
 
+
     // MIDI ----------------------------------------------------------------
 
     // Creates a platform dependent WebMIDIAccessor. MIDIAccessor under platform
     // creates and owns it.
     virtual WebMIDIAccessor* createMIDIAccessor(WebMIDIAccessorClient*) { return 0; }
 
+
     // Blob ----------------------------------------------------------------
 
     // Must return non-null.