libmediaplayerservice: 64-bit compile warnings

Change-Id: I333e52dc377becc774f3fa971c230ecb55ea8d7b
diff --git a/media/libmediaplayerservice/MidiFile.cpp b/media/libmediaplayerservice/MidiFile.cpp
index deeddd1..749ef96 100644
--- a/media/libmediaplayerservice/MidiFile.cpp
+++ b/media/libmediaplayerservice/MidiFile.cpp
@@ -114,7 +114,7 @@
 }
 
 status_t MidiFile::setDataSource(
-        const sp<IMediaHTTPService> &httpService,
+        const sp<IMediaHTTPService> & /*httpService*/,
         const char* path,
         const KeyedVector<String8, String8> *) {
     ALOGV("MidiFile::setDataSource url=%s", path);