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

LayoutTests/webmidi/implicit-open-expected.txt

+Tests MIDIPort implicit open.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS requestMIDIAccess() succeeded with access [object MIDIAccess].
+Check state transition for setonmidimessage on closed state.
+- check initial state.
+PASS port.connection is "closed"
+- check port handler.
+PASS handler is called with port [object MIDIInput].
+PASS eventport.id is "MockInputID"
+PASS eventport.connection is "open"
+- check access handler.
+PASS handler is called with port [object MIDIInput].
+PASS eventport.id is "MockInputID"
+PASS eventport.connection is "open"
+- check final state.
+PASS port.connection is "open"
+Check state transition for send on closed state.
+- check initial state.
+PASS port.connection is "closed"
+- check port handler.
+PASS handler is called with port [object MIDIOutput].
+PASS eventport.id is "MockOutputID"
+PASS eventport.connection is "open"
+- check access handler.
+PASS handler is called with port [object MIDIOutput].
+PASS eventport.id is "MockOutputID"
+PASS eventport.connection is "open"
+- check final state.
+PASS port.connection is "open"
+PASS successfullyParsed is true
+
+TEST COMPLETE
+