Adding ArcBridge Interface for Volume Update Requests

components/arc/common/audio.mojom

Index: components/arc/common/audio.mojom
diff --git a/components/arc/common/audio.mojom b/components/arc/common/audio.mojom
index 39e02ec514a7a0ee12263a2127259bd479d6876d..346fb3019ce55dc917ba55632dc283c2e88ea7ce 100644
--- a/components/arc/common/audio.mojom
+++ b/components/arc/common/audio.mojom
@@ -2,7 +2,7 @@
 // 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;
 
@@ -13,9 +13,14 @@ enum AudioSwitch {
   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);

[Luis Héctor Chávez, 2017/04/13 14:21:25]

nit: OnSystemVolumeUpdateRequest

Also mention that this is a privileged API and should only be used on
whitelisted cases.

[dcheng, 2017/04/13 18:02:40]

Can you clarify what that means? We have no way of enforcing that from the
browser process, right? So really anyone can call it.

[Luis Héctor Chávez, 2017/04/13 18:05:40]

Yes, we're trusting that the other side will only call this in appropriate
occasions. Otherwise random apps will be able to modify the system volume and
we'd like to avoid that. The best we can do here is document the intended usage.

[yueli, 2017/06/02 19:10:13]

Done.

 };
 
 // Next method ID: 3