mediaplayer: add buffering settings API

Test: compiles, checked that params is passed all the way to source.
Bug:32524218
Change-Id: I637d1ab09f94a3830a33a39e7e9f1b3efb22357f
diff --git a/include/media/BufferingSettings.h b/include/media/BufferingSettings.h
index 281a5c1..e812d2a 100644
--- a/include/media/BufferingSettings.h
+++ b/include/media/BufferingSettings.h
@@ -66,6 +66,7 @@
     status_t writeToParcel(Parcel* parcel) const override;
     status_t readFromParcel(const Parcel* parcel) override;
 
+    String8 toString() const;
 };
 
 } // namespace android