Fix Widevine classic playback errors with NuPlayer

bug: 17589961
Change-Id: If16c61b90cf92caa89eecd66aabef5813fd7619b
diff --git a/media/libmediaplayerservice/nuplayer/GenericSource.cpp b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
index bd75034..f84decd 100644
--- a/media/libmediaplayerservice/nuplayer/GenericSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
@@ -1198,10 +1198,17 @@
     switch (trackType) {
         case MEDIA_TRACK_TYPE_VIDEO:
             track = &mVideoTrack;
+            if (mIsWidevine) {
+                maxBuffers = 2;
+            }
             break;
         case MEDIA_TRACK_TYPE_AUDIO:
             track = &mAudioTrack;
-            maxBuffers = 64;
+            if (mIsWidevine) {
+                maxBuffers = 8;
+            } else {
+                maxBuffers = 64;
+            }
             break;
         case MEDIA_TRACK_TYPE_SUBTITLE:
             track = &mSubtitleTrack;