Yes, the part of thems does not work fully.

Chrome and SRWare Iron work First API and show notification dialog.

And Opera preferenses has no effections with following setting.

%appdata%\Opera Software\Opera StablePreferences

"profile": {
"content_settings": {
"clear_on_exit_migrated": true,
"pattern_pairs": {
"https://dl.dropboxusercontent.com:443,https://dl.dropboxusercontent.com:443": {
"midi-sysex": 1
}
},
"pref_version": 1
},

chrome://flags/#enable-web-midi

at first turn on MIDI API.

But Opera does not show Notification Dialog with using MIDI API

https://dl.dropboxusercontent.com/u/695740/WebMusicDevelopersJP/WebMIDIAPITest/index.html

So that Opera can not work MIDI API Applications.