Use the music note icon for the music files pref.

Change-Id: I0e688321d7697aa4ad5b4ae16e7ca03f60e582cd
Fixes: 36900603
Test: Manual

res/drawable/ic_media_stream_on_24dp.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (C) 2017 The Android Open Source Project
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  -->
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M18,3h-5c-0.55,0 -1,0.45 -1,1v8.3a3.88,3.88 0,0 0,-2.9 -0.04c-1.79,0.67 -3.11,2.35 -3.1,4.26A4.483,4.483 0,0 0,10.5 21c2.5,0 4.5,-2.3 4.5,-4.5V6h3c0.55,0 1,-0.45 1,-1V4c0,-0.55 -0.45,-1 -1,-1z"/>
+</vector>

src/com/android/settings/applications/MusicViewHolderController.java

@@ -61,7 +61,7 @@ public class MusicViewHolderController implements FileViewHolderController {
 
     @Override
     public void setupView(AppViewHolder holder) {
-        holder.appIcon.setImageDrawable(mContext.getDrawable(R.drawable.empty_icon));
+        holder.appIcon.setImageDrawable(mContext.getDrawable(R.drawable.ic_media_stream_on_24dp));
         holder.appName.setText(mContext.getText(R.string.audio_files_title));
         holder.summary.setText(Formatter.formatFileSize(mContext, mMusicSize));
     }