Prepare for handling several sources of idleness.
Make idle callbacks aware of nsITimers.
Add pref for how far into the timer queue.
1311425 - Avoid expiration timers when scheduling idle runnables.
review comment fix to ensure low priority timers aren't taken into account when calling NS_GetTimerDeadlineHintOnCurrentThread.
Since these are just interpreted comments, there's 0 impact on actual code.
This removes all lines that match /* vim: set(.*)tw=80: */ with S&R -- there are
a few others scattered around which will be removed manually in a second part.
