Web MIDI: implement implicit open() on send() and setOnmidimessage()

Source/modules/webmidi/MIDIInput.cpp

Index: Source/modules/webmidi/MIDIInput.cpp
diff --git a/Source/modules/webmidi/MIDIInput.cpp b/Source/modules/webmidi/MIDIInput.cpp
index 45da45e39b8ac4e5cc3e3584de1e75edfc0726e7..68317d04edce5c95dd3e6759c775d5b592c5884e 100644
--- a/Source/modules/webmidi/MIDIInput.cpp
+++ b/Source/modules/webmidi/MIDIInput.cpp
@@ -50,6 +50,20 @@ MIDIInput::MIDIInput(MIDIAccess* access, const String& id, const String& manufac
 {
 }
 
+EventListener* MIDIInput::onmidimessage()
+{
+    return getAttributeEventListener(EventTypeNames::midimessage);
+}
+
+void MIDIInput::setOnmidimessage(PassRefPtr<EventListener> listener)
+{
+    // Implicit open. It does nothing if the port is already opened.
+    // See http://www.w3.org/TR/webmidi/#widl-MIDIPort-open-Promise-MIDIPort
+    open();
+
+    setAttributeEventListener(EventTypeNames::midimessage, listener);
+}
+
 void MIDIInput::didReceiveMIDIData(unsigned portIndex, const unsigned char* data, size_t length, double timeStamp)
 {
     ASSERT(isMainThread());
@@ -57,6 +71,9 @@ void MIDIInput::didReceiveMIDIData(unsigned portIndex, const unsigned char* data
     if (!length)
         return;
 
+    if (getConnection() != ConnectionStateOpen)
+        return;
+
     // Drop sysex message here when the client does not request it. Note that this is not a security check but an
     // automatic filtering for clients that do not want sysex message. Also note that sysex message will never be sent
     // unless the current process has an explicit permission to handle sysex message.