Add a mixin for registering key bindings.
Review Request #4251 — Created June 19, 2013 and submitted
Add a mixin for registering key bindings. KeyBindingsMixin makes it easy to map keys in a view to functions. Any view using this mixin will listen for key presses matching any of the keys listed in the View.keyBindings map, and call the appropriate function.
Tested manually with my upcoming diff viewer change. Unit tests pass.