Web MIDI: MIDIAccessor platform implementation and Blink API

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index de31d2a3ee301c215f2d6069ad4edca9b9debdc4..f3d03d57340386f07ddfee09d2ed89abb5c2de9d 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -66,6 +66,8 @@ class WebGestureCurve;
 class WebGraphicsContext3DProvider;
 class WebHyphenator;
 class WebIDBFactory;
+class WebMIDIAccessor;
+class WebMIDIAccessorClient;
 class WebMediaStreamCenter;
 class WebMediaStreamCenterClient;
 class WebMessagePortChannel;
@@ -151,6 +153,9 @@ 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 ----------------------------------------------------------------
+
+    virtual WebMIDIAccessor* createMIDIAccessor(WebMIDIAccessorClient*) { return 0; }
 
     // Blob ----------------------------------------------------------------