generateUID wasnt quite dead

Original commit Ifdb9e1b24f618d7be388ea0e50ccb6ee69d7f5ca removed
the generateUID helper, but it was used in one place to give
onscreen timestamps a unique identifier.

Change-Id: I5ba076696ebb0d1f70ab24ef04ef0c33a8813a8e
Merge "generateUID wasnt quite dead"