Web MIDI: introduce WebMIDIClient API to request a permission

Source/modules/webmidi/MIDIAccess.h

Index: Source/modules/webmidi/MIDIAccess.h
diff --git a/Source/modules/webmidi/MIDIAccess.h b/Source/modules/webmidi/MIDIAccess.h
index 595afceabf03f5a2aa90ec187998a4bdfa0e3877..41fc4b697f4e2085c567a62102be5b2aa2cb25e0 100644
--- a/Source/modules/webmidi/MIDIAccess.h
+++ b/Source/modules/webmidi/MIDIAccess.h
@@ -61,6 +61,8 @@ public:
     DEFINE_ATTRIBUTE_EVENT_LISTENER(connect);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(disconnect);
 
+    void enableSysEx(bool enable);
+
     // EventTarget
     virtual const AtomicString& interfaceName() const OVERRIDE { return eventNames().interfaceForMIDIAccess; }
     virtual ScriptExecutionContext* scriptExecutionContext() const OVERRIDE { return ActiveDOMObject::scriptExecutionContext(); }
@@ -79,6 +81,8 @@ public:
 private:
     explicit MIDIAccess(ScriptExecutionContext*, MIDIAccessPromise*);
 
+    void startRequest();
+
     // EventTarget
     virtual void refEventTarget() OVERRIDE { ref(); }
     virtual void derefEventTarget() OVERRIDE { deref(); }
@@ -92,6 +96,8 @@ private:
 
     OwnPtr<MIDIAccessor> m_accessor;
     bool m_hasAccess;
+    bool m_enableSysEx;
+    bool m_requesting;
 };
 
 } // namespace WebCore