Browser windows (and app windows in the multi-profile case) have context menus that are shown when the user right clicks on the header/frame area. Currently this is unimplemented w/Mash, so there are no context menus for the header.

Some options that come to mind:

1. make the client responsible for the header, as previously discussed, but then window dragging would probably break and have to be dealt with somehow. Same for window resizing, perhaps.
2. have Ash tell the client to run a context menu. This might not work well given that context menus need to handle various sequences of mouse press, release, drag, etc.
3. create an interface where the client sets a list of context menu items, Ash runs the context menu and when an item is selected, informs the client
4. Let clients have first crack at events in non-client area, and then send them to ash when they're not handled by the client