[Rlog78b] Make log privacy filtering decisions on n-grams

Previously, words were pushed out of a LogBuffer one at a time.  The receiving code had to keep
state to know whether a n-gram was safe to log.  This patch looks at the entire n-gram and makes a
single decision based on it alone.

mult-project commit with I3c40d7e02c77943d2668094ddb1d03efb942c74f

Change-Id: Id7d90bbd551b1a2f4e0e35f38852652f68f273f8