NuPlayerRenderer: work around some racing condition in audio track

Test: no more super long delay when seeking/pausing/resuming
Bug: 66917327
Change-Id: Ic43ef543984f299d6ea7197c9e55d76518474c8a
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp
index dec17e2..a568a17 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp
@@ -549,8 +549,10 @@
                 CHECK_EQ(mAudioSink->getPosition(&numFramesPlayed),
                          (status_t)OK);
 
+                // Handle AudioTrack race when start is immediately called after flush.
                 uint32_t numFramesPendingPlayout =
-                    mNumFramesWritten - numFramesPlayed;
+                    (mNumFramesWritten > numFramesPlayed ?
+                        mNumFramesWritten - numFramesPlayed : 0);
 
                 // This is how long the audio sink will have data to
                 // play back.