Switch to "tests" instead of "optional" for build.

Change-Id: Iaea3819c18be34b5c3864015316b67397c928f2d
diff --git a/tests/RenderScriptTests/ModelViewer/Android.mk b/tests/RenderScriptTests/ModelViewer/Android.mk
index 1d9bacf..18ceac5 100644
--- a/tests/RenderScriptTests/ModelViewer/Android.mk
+++ b/tests/RenderScriptTests/ModelViewer/Android.mk
@@ -17,7 +17,7 @@
 LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 
-LOCAL_MODULE_TAGS := optional
+LOCAL_MODULE_TAGS := tests
 
 LOCAL_SRC_FILES := $(call all-java-files-under, src) $(call all-renderscript-files-under, src)
 #LOCAL_STATIC_JAVA_LIBRARIES := android.renderscript