Web MIDI: implement MIDIInput

Source/modules/webmidi/MIDIInput.idl

Index: Source/modules/webmidi/MIDIInput.idl
diff --git a/Source/modules/quota/StorageErrorCallback.idl b/Source/modules/webmidi/MIDIInput.idl
similarity index 93%
copy from Source/modules/quota/StorageErrorCallback.idl
copy to Source/modules/webmidi/MIDIInput.idl
index 0d65450be7bc64e37ccc6014ff09e46f039f4379..f4cd4f2be6010c47e53d41764a3ff4627509a51f 100644
--- a/Source/modules/quota/StorageErrorCallback.idl
+++ b/Source/modules/webmidi/MIDIInput.idl
@@ -28,6 +28,9 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-callback interface StorageErrorCallback {
-    boolean handleEvent(DOMCoreException error);
+[
+    ActiveDOMObject,
+    EventTarget

[haraken, 2013/05/02 09:06:57]

Another option is to have MIDIPort inherit EventTarget (this is a desirable
solution in terms of the IDL spec), but it might not work due to lack of
implementation support for EventTarget. I'm OK with this change for now.

+] interface MIDIInput : MIDIPort {
+    attribute EventListener onmidimessage;
 };