This code now lives in TimeoutManager. Note that this is a transition
state, the Timeout list management code also needs to be refactored out
later.
In order to simplify the lifetime management of the new class, its
lifetime is equal to the lifetime of its containing nsGlobalWindow. In
a few places where we need to dispatch runnables to do asynchronous work
on this object, we hold the containing window alive to guarantee safety.
This patch also removes a bit of dead code that was left over from the
code removed in bug 1281793. See:
https://hg.mozilla.org/mozilla-central/rev/0ac748f4d677#l1.63
