The update optimization will not visit child nodes unless the
parent has any refresh flags set. However if a "partial update"
occurs which only clears some of the flags (e.g. getWorldBound()),
then a situation could occur where a child node has refresh
flags set but not its parent, thus causing the aformentioned issue.
To allieviate this, we must always propagate the specific flag
required, regardless of whether or not the parent has some other
flags already set.
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