Backport the AudioPreview activity from Music2 to Music

Change-Id: I1e1ec54a4613ef60e9a4539d5c50ed0874764b93
diff --git a/Android.mk b/Android.mk
index 2a8f16e..a537886 100644
--- a/Android.mk
+++ b/Android.mk
@@ -10,6 +10,8 @@
 
 LOCAL_SDK_VERSION := 8
 
+LOCAL_PROGUARD_FLAGS := -include $(LOCAL_PATH)/proguard.flags
+
 include $(BUILD_PACKAGE)
 
 # Use the folloing include to make our test apk.