Making way for dynamic isActive method on Context.  First we cannot hurt
performance so we are asking the implementation if isActive is permanently
returning true.  Most will answer "yes" to this question, in which case we
can continue to cache the result as we do now.  If the answer to this
question is "no" then we are going to have to do something different
since the isActive method can return different values at different times,
something that currently doesn't work properly