getUserMedia: handle the device starting status report.

chrome/test/data/extensions/api_test/desktop_capture/test.js

 // 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.
 
 function onPickerResult(audio_track_num, id, options) {
   chrome.test.assertEq("string", typeof id);
   chrome.test.assertTrue(id != "");
   var video_constraint = { mandatory: { chromeMediaSource: "desktop",
                                         chromeMediaSourceId: id } };
   var audio_constraint =
@@ skipping 116 matching lines @@
   // permission and the source type, it may or may not actually get the audio
   // track.
   // In detail:
   //  1. We cannot support audio for Window share;
   //  2. We can support audio for Tab share;
   //  3. We can support audio for Screen share on Windows;
   //  4. We can support audio for Screen Share on ChromeOS if USE_CRAS is on;
   //  5. To actually get audio track, user permission is always necessary;
   //  6. To actually get audio track, getUserMedia() should set audio
   //     constraint.
+  function screenShareWithAudioPermissionGetStream() {
+    chrome.desktopCapture.chooseDesktopMedia(
+        ["screen", "audio"],
+        onPickerResult.bind(undefined,
+                            expected_audio_tracks_for_screen_share));
+  },
+
+  function screenShareWithoutAudioPermissionGetStream() {
+    chrome.desktopCapture.chooseDesktopMedia(
+        ["screen", "audio"], onPickerResult.bind(undefined, 0));
+  }
+
+  /**

[Sergey Ulanov, 2017/03/14 19:43:34]

use // for comments please
And then you also wouldn't have to move any tests.

+   * Only screenShare can be tested as above, because "chooseDesktopMedia" will
+   * return fake source id to tab/windowShare, with which tab/window catpure
+   * can't be started successfully.
+   * TODO(braveyao): get below cases working again. http://crbug.com/699201
   function tabShareWithAudioPermissionGetStream() {
     chrome.desktopCapture.chooseDesktopMedia(
         ["tab", "audio"], onPickerResult.bind(undefined, 1));
   },
 
   function windowShareWithAudioPermissionGetStream() {
     chrome.desktopCapture.chooseDesktopMedia(
         ["window", "audio"], onPickerResult.bind(undefined, 0));
   },
 
-  function screenShareWithAudioPermissionGetStream() {
-    chrome.desktopCapture.chooseDesktopMedia(
-        ["screen", "audio"],
-        onPickerResult.bind(undefined,
-                            expected_audio_tracks_for_screen_share));
-  },
-
   function tabShareWithoutAudioPermissionGetStream() {
     chrome.desktopCapture.chooseDesktopMedia(
         ["tab", "audio"], onPickerResult.bind(undefined, 0));
   },
 
   function windowShareWithoutAudioPermissionGetStream() {
     chrome.desktopCapture.chooseDesktopMedia(
         ["window", "audio"], onPickerResult.bind(undefined, 0));
-  },
+  }
+   **/
 
-  function screenShareWithoutAudioPermissionGetStream() {
-    chrome.desktopCapture.chooseDesktopMedia(
-        ["screen", "audio"], onPickerResult.bind(undefined, 0));
-  }
 ]);