Start to use app fuse in MtpDocumentsProvider.

BUG=25756419

Change-Id: I050e7cf7523926710291875737602e95c47be088
diff --git a/packages/MtpDocumentsProvider/Android.mk b/packages/MtpDocumentsProvider/Android.mk
index 67bbf78..b31b0b1 100644
--- a/packages/MtpDocumentsProvider/Android.mk
+++ b/packages/MtpDocumentsProvider/Android.mk
@@ -7,6 +7,7 @@
 LOCAL_CERTIFICATE := media
 LOCAL_PRIVILEGED_MODULE := true
 LOCAL_JNI_SHARED_LIBRARIES := libappfuse_jni
+LOCAL_PROGUARD_FLAG_FILES := proguard.flags
 
 include $(BUILD_PACKAGE)
 include $(call all-makefiles-under, $(LOCAL_PATH))