Instead of keeping track of the fraction of time that we're

Instead of keeping track of the fraction of time that we're
idle, keep track of the fraction of time we're not idle.  This
works better because the default processor state is idle, and
the default stat value is 0.
Keep the stat as idleFraction which is a formula that is equal
to 1 - notIdleFraction

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extra : convert_revision : 331c2e46f45ae0abda46988567ac2c4f7c42ccad