1) Prevent it from "bouncing" which happens when we queue up a lot of
open and close events. Stop any running animations before starting
new ones. This fixes#1340.
2) Prevent a bug that's not really visible to the user where we wind
up re-initializing a context menu over and over which results in us
binding tons of hover events. I don't think this causes any serious
damage, but it's probably not good.