Change the description of chrome.audio api

The API is only available in kiosk mode, but the documentation does not specify
that.

Bug: 1099688
Change-Id: Ia0d067d77d4fc75991e447c59ff77d9595ff8e11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2398623Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Anatoliy Potapchuk <apotapchuk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805097}

extensions/common/api/audio.idl

@@ -4,7 +4,8 @@
 
 // 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.
+// system.
+// This API is currently only available in kiosk mode for ChromeOS.
 namespace audio {
 
   // Type of stream an audio device provides.

third_party/closure_compiler/externs/audio.js

-// Copyright 2018 The Chromium Authors. All rights reserved.
+// Copyright 2020 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.
 
@@ -11,9 +11,7 @@
 
 /** @fileoverview Externs generated from namespace: audio */
 
-/**
- * @const
- */
+/** @const */
 chrome.audio = {};
 
 /**
@@ -44,6 +42,7 @@ chrome.audio.DeviceType = {
   LINEOUT: 'LINEOUT',
   POST_MIX_LOOPBACK: 'POST_MIX_LOOPBACK',
   POST_DSP_LOOPBACK: 'POST_DSP_LOOPBACK',
+  ALSA_LOOPBACK: 'ALSA_LOOPBACK',
   OTHER: 'OTHER',
 };
 
@@ -135,10 +134,10 @@ chrome.audio.LevelChangedEvent;
 
 /**
  * Gets a list of audio devices filtered based on |filter|.
- * @param {!chrome.audio.DeviceFilter} filter Device properties by which to
- *     filter the list of returned     audio devices. If the filter is not set
- *     or set to <code>{}</code>,     returned device list will contain all
- *     available audio devices.
+ * @param {?chrome.audio.DeviceFilter|undefined} filter Device properties by
+ *     which to filter the list of returned     audio devices. If the filter is
+ *     not set or set to <code>{}</code>,     returned device list will contain
+ *     all available audio devices.
  * @param {function(!Array<!chrome.audio.AudioDeviceInfo>): void} callback
  *     Reports the requested list of audio devices.
  * @see https://developer.chrome.com/extensions/audio#method-getDevices