Web MIDI: clean up on MIDIPort and MIDIErrorCallback

Source/modules/webmidi/MIDIPort.idl

Index: Source/modules/webmidi/MIDIPort.idl
diff --git a/Source/modules/webmidi/MIDIPort.idl b/Source/modules/webmidi/MIDIPort.idl
index 2c7286fbc22875f02f9157e4d3389d85e49a1e8f..226387cb79bd5825f319434d94eaf5f4135610e8 100644
--- a/Source/modules/webmidi/MIDIPort.idl
+++ b/Source/modules/webmidi/MIDIPort.idl
@@ -28,12 +28,10 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-// FIXME: IDL generator doesn't support readonly enum yet.
-// See also, http://crbug.com/234925
-//enum MIDIPortType {
-//    "input",
-//    "output"
-//};
+enum MIDIPortType {
+    "input",
+    "output"
+};
 
 [
     ActiveDOMObject,
@@ -42,7 +40,7 @@
     readonly attribute DOMString id;
     readonly attribute DOMString manufacturer;
     readonly attribute DOMString name;
-    readonly attribute DOMString type;
+    readonly attribute MIDIPortType type;
     readonly attribute DOMString version;
 
     attribute EventListener ondisconnect;