Web MIDI: add blink APIs to notify device connection events

Source/modules/webmidi/MIDIPort.h

Index: Source/modules/webmidi/MIDIPort.h
diff --git a/Source/modules/webmidi/MIDIPort.h b/Source/modules/webmidi/MIDIPort.h
index 4e4f31fe262cd850c2f6371f4eb557ecc2c24d11..23817db0eab869c1fefd85f0ccdb8968883a5140 100644
--- a/Source/modules/webmidi/MIDIPort.h
+++ b/Source/modules/webmidi/MIDIPort.h
@@ -57,6 +57,8 @@ public:
     String version() const { return m_version; }
 
     MIDIAccess* midiAccess() const { return m_access; }
+    bool isActive() const { return m_active; }
+    void setActiveState(bool active) { m_active = active; }
 
     virtual void trace(Visitor*) override;
 
@@ -67,7 +69,7 @@ public:
     virtual ExecutionContext* executionContext() const override final;
 
 protected:
-    MIDIPort(MIDIAccess*, const String& id, const String& manufacturer, const String& name, MIDIPortTypeCode, const String& version);
+    MIDIPort(MIDIAccess*, const String& id, const String& manufacturer, const String& name, MIDIPortTypeCode, const String& version, bool active);
 
 private:
     String m_id;
@@ -76,6 +78,7 @@ private:
     MIDIPortTypeCode m_type;
     String m_version;
     Member<MIDIAccess> m_access;
+    bool m_active;
 };
 
 } // namespace blink