Ensure getPlaybackHeadPosition isn't called if not needed

Once the value returned from AudioTimestampPoller advances, we
only need getPlaybackHeadPosition to sample sync params and
verify the returned timestamp. Both of these happen less often
and we can avoid calling getPlaybackHeadPosition if we don't
actually need it.

PiperOrigin-RevId: 512882170
(cherry picked from commit 4cf7d3c7)

library/core/src/main/java/com/google/android/exoplayer2/audio/AudioTrackPositionTracker.java

@@ -451,13 +451,13 @@ import java.lang.reflect.Method;
   }
 
   private void maybeSampleSyncParams() {
-    long playbackPositionUs = getPlaybackHeadPositionUs();
-    if (playbackPositionUs == 0) {
-      // The AudioTrack hasn't output anything yet.
-      return;
-    }
     long systemTimeUs = System.nanoTime() / 1000;
     if (systemTimeUs - lastPlayheadSampleTimeUs >= MIN_PLAYHEAD_OFFSET_SAMPLE_INTERVAL_US) {
+      long playbackPositionUs = getPlaybackHeadPositionUs();
+      if (playbackPositionUs == 0) {
+        // The AudioTrack hasn't output anything yet.
+        return;
+      }
       // Take a new sample and update the smoothed offset between the system clock and the playhead.
       playheadOffsets[nextPlayheadOffsetIndex] =
           Util.getPlayoutDurationForMediaDuration(playbackPositionUs, audioTrackPlaybackSpeed)
@@ -479,11 +479,11 @@ import java.lang.reflect.Method;
       return;
     }
 
-    maybePollAndCheckTimestamp(systemTimeUs, playbackPositionUs);
+    maybePollAndCheckTimestamp(systemTimeUs);
     maybeUpdateLatency(systemTimeUs);
   }
 
-  private void maybePollAndCheckTimestamp(long systemTimeUs, long playbackPositionUs) {
+  private void maybePollAndCheckTimestamp(long systemTimeUs) {
     AudioTimestampPoller audioTimestampPoller = checkNotNull(this.audioTimestampPoller);
     if (!audioTimestampPoller.maybePollTimestamp(systemTimeUs)) {
       return;
@@ -492,6 +492,7 @@ import java.lang.reflect.Method;
     // Check the timestamp and accept/reject it.
     long audioTimestampSystemTimeUs = audioTimestampPoller.getTimestampSystemTimeUs();
     long audioTimestampPositionFrames = audioTimestampPoller.getTimestampPositionFrames();
+    long playbackPositionUs = getPlaybackHeadPositionUs();
     if (Math.abs(audioTimestampSystemTimeUs - systemTimeUs) > MAX_AUDIO_TIMESTAMP_OFFSET_US) {
       listener.onSystemTimeUsMismatch(
           audioTimestampPositionFrames,