The ctrl-d binding is dangerous as it removes the unsaved draft comment
without confirmation and is a common keybinding when editing text (it is
the emacs binding for forward-delete). Esc can still be used to discard
unsaved draft comments; removing saved draft comments will now require
using the mouse.
Change-Id: I30120351f4be0a09ad9404d352fde1408982c05f
a38cf206ed