dvr_api GetExternalSurface returns ANativeWindow

Now that we have a public NDK API to convert an ANativeWindow to a Java
Surface, we no longer need to mess with Jni and libandroid_runtime in
libdvr.

See more information at:
http://ag/#/q/topic:ANativeWindow_toSurface+(status:open+OR+status:merged)

Also, as a side effect, we are now free to convert this library to use
Android.bp (though we probably want to hold off for a while).

Bug: 36266201
Test: Built and ran dvr_buffer_queue-test
Change-Id: Ia0f6a8735c7d508195c30e3c7d040791e13a6ce3
diff --git a/libs/vr/libdvr/tests/Android.mk b/libs/vr/libdvr/tests/Android.mk
index 158d58f..75e2a7d 100644
--- a/libs/vr/libdvr/tests/Android.mk
+++ b/libs/vr/libdvr/tests/Android.mk
@@ -9,6 +9,7 @@
     libhardware \
     libui \
     libutils \
+    libnativewindow \
 
 static_libraries := \
     libdvr \