Consider all of the following:

• HTMLMenuElement
• HTMLButtonElement.prototype.menu / menu content attribute / <button menu="id">
• HTMLElement.prototype.contextMenu / contextmenu content attribute
• <menu type="contextmenu"> functionality (renamed in Rename <menu type=popup> to <menu type=context> #235)
  • HTMLMenuItemElement
• <menu type="toolbar"> functionality
• The "command" concept
  • Uniformizing menu items, buttons, and links as a spec-level device (this is probably a good thing, unless it drastically contradicts implementations)
  • The command API (removed in Remove some unimplemented menu and command features #244)
  • document.commands (removed in Remove some unimplemented menu and command features #244)
  • master/slave commands via <menuitem command=""> (removed in Remove some unimplemented menu and command features #244)

Which of these are actually on track to be implemented? I know Gecko has some implementation of menu stuff, although based on an older spec. And Blink has a behind-a-flag implementation of contextmenu, and maybe more.

I am especially interested in <menu type="toolbar"> and the command API. Are they implemented anywhere, or on track to be implemented? If not, we could remove a decent amount of extra complication.