Add MODIFY_AUDIO_SETTINGS permission in Android manifest and implementation in audio manager.

media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java

Index: media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java
===================================================================
--- media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java	(revision 0)
+++ media/base/android/java/src/org/chromium/media/AudioManagerAndroid.java	(revision 0)
@@ -0,0 +1,23 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.media;
+
+import android.content.Context;
+import android.media.AudioManager;
+
+import org.chromium.base.CalledByNative;
+import org.chromium.base.JNINamespace;
+
+@JNINamespace("media")
+class AudioManagerAndroid {
+    @CalledByNative
+    public static void setMode(Context context, int mode) {
+        AudioManager audioManager =
+                (AudioManager)context.getSystemService(Context.AUDIO_SERVICE);
+        if (null != audioManager) {
+            audioManager.setMode(mode);
+        }
+    }
+}