Adding ArcBridge Interface for Volume Update Requests

components/arc/common/audio.mojom

 // Copyright 2016 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.
 
-// Next MinVersion: 3
+// Next MinVersion: 4
 
 module arc.mojom;
 
 // Use same switch values as kernel switch events.
 [Extensible]
 enum AudioSwitch {
   SW_HEADPHONE_INSERT = 0x02,
   SW_MICROPHONE_INSERT = 0x04
 };
 
+// Next method ID:2
 interface AudioHost {
   // Tells the host to show the volume controls.
   ShowVolumeControls@0();
+
+  // Request that the volume be changed to |volume|
+  // |volume| is of the range [0. 100]
+  [MinVersion=3] OnVolumeUpdateRequest@1(float volume);
 };
 
 // Next method ID: 3
 interface AudioInstance {
   // Establishes full-duplex communication with the host.
   [MinVersion=1] Init@1(AudioHost host);
 
   // Notify plug states of headphone, microphone, etc.  Each switch state is
   // represented by the corresponding bit, if the bit is set then the switch
   // is plugged/inserted.
   NotifySwitchState@0(uint32 state);
 
   // Notify volume and mute state.
   // volume ranges from 0 to 100.
   // muted == true if audio is muted.
   [MinVersion=2] NotifyVolumeState@2(uint32 volume, bool muted);
 };