MediaPlayerTest: use getAnchorSytemNanoTime() instead of raw field.

Change-Id: I1bc9654c4fd0dc065a73de79acc9e473afbfacda
diff --git a/tests/tests/media/src/android/media/cts/MediaPlayerTest.java b/tests/tests/media/src/android/media/cts/MediaPlayerTest.java
index 18cd353..86f0313 100644
--- a/tests/tests/media/src/android/media/cts/MediaPlayerTest.java
+++ b/tests/tests/media/src/android/media/cts/MediaPlayerTest.java
@@ -896,7 +896,7 @@
         assertEquals("MediaPlayer had error in clockRate " + ts1.getMediaClockRate(),
                 playbackRate, ts1.getMediaClockRate(), 0.001f);
         assertTrue("The nanoTime of Media timestamp should be taken when getTimestamp is called.",
-                nt1 <= ts1.nanoTime && ts1.nanoTime <= nt2);
+                nt1 <= ts1.getAnchorSytemNanoTime() && ts1.getAnchorSytemNanoTime() <= nt2);
 
         mMediaPlayer.pause();
         ts1 = mMediaPlayer.getTimestamp();