Update audio api to use v2 stable device ID

extensions/common/api/audio.idl

 // Copyright (c) 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.
 
 // The <code>chrome.audio</code> API is provided to allow users to
 // get information about and control the audio devices attached to the
 // system. This API is currently only implemented for ChromeOS.
 namespace audio {
 
   dictionary OutputDeviceInfo {
@@ skipping 34 matching lines @@
     // The user-friendly name (e.g. "USB Microphone").
     DOMString displayName;
     // Device name.
     DOMString deviceName;
     // True if this is the current active device.
     boolean isActive;
     // True if this is muted.
     boolean isMuted;
     // The sound level of the device, volume for output, gain for input.
     long level;
-    // The stable/persisted device id string when available.
+    // The stable/persisted device id string.
+    DOMString stableId;

[Devlin, 2016/12/20 18:15:45]

This is kind of a shame - we now have 3 different ids on this single object.  Is
there no way we can do this opaquely to the developer?

[tbarzic, 2016/12/20 18:51:20]

I guess we could, but at cost of the app losing information previously saved in
their storage (which was the goal of introducing stableDeviceId in the first
place).

Note that this API is still in dev, and currently used by a single app. I plan
to expose deprecated stableDeviceId only to the current whitelist, and
eventually remove it altogether.

[Devlin, 2016/12/20 19:36:17]

That makes it better.  If that's the case, can we just reach out to that app and
say "by the way, this is gone"?  Or do we really need this transition period?

[tbarzic, 2016/12/20 19:53:56]

We could, but imho it would be better to provide the app a chance to update
their stored mapping from stableDeviceId to device properties.

Adding +mnilsson to check if we could get away with just replacing stable IDs
(without providing a transitional period where both deprecated and new stable ID
are exposed).

+
+    // Deprecated version of stable audio device ID. Available for backward
+    // compatibility - usages should be migrated to |stableId|.
+    [deprecated = "Use |stableId|."]
     DOMString? stableDeviceId;
   };
 
   dictionary DeviceProperties {
     // True if this is muted.
     boolean isMuted;
     // If this is an output device then this field indicates the output volume.
     // If this is an input device then this field is ignored.
     double? volume;
     // If this is an input device then this field indicates the input gain.
@@ skipping 40 matching lines @@
     // |isInput|: true indicating audio input; false indicating audio output.
     // |isMuted|: new value of mute state.
     static void OnMuteChanged(boolean isInput, boolean isMuted);
 
     // Fired when audio devices change, either new devices being added, or
     // existing devices being removed.
     // |devices|: List of all present audio devices after the change.
     static void OnDevicesChanged(AudioDeviceInfo[] devices);
   };
 };