HdrViewfinder time stamp always 0

[v-hogood]

See https://issuetracker.google.com/issues/181521870

If I log the time stamp like so it is always 0:

            // Get to newest input
            for (int i = 0; i < pendingFrames; i++) {
                mInputAllocation.ioReceive();
                Log.i(TAG, "timeStamp: " + mInputAllocation.getTimeStamp());
            }