Correctly handle enumerations for AudioManagers that report only the default audio output device.

content/browser/renderer_host/media/media_stream_manager.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/renderer_host/media/media_stream_manager.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
 #include <cctype>
@@ skipping 721 matching lines @@
   }
   DVLOG(1) << "Enumerate Devices ({label = " << label <<  "})";
 }
 
 void MediaStreamManager::AudioOutputDevicesEnumerated(
     const AudioOutputDeviceEnumeration& device_enumeration) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DVLOG(1) << "AudioOutputDevicesEnumerated()";
   StreamDeviceInfoArray device_infos;
 
-  // If the enumeration contains only one entry, it means there are no devices.
-  // The single entry contains default parameters from the audio manager.
-  if (device_enumeration.size() > 1) {

[tommi (sloooow) - chröme, 2016/01/19 13:03:37]

instead of the 'has_actual_devices' member variable, could we have a method like
so:

bool has_actual_devices() const {
  // <include comment>
  return devices.size() > 1;
}

?

[Guido Urdaneta, 2016/01/19 13:41:10]

devices.size() > 1 is incorrect for AudioManagers that always report only one
device.
The has_actual_devices field allows differentiating that from the case where
there are no devices (but where we have one entry with the default parameters).
I updated the AudioOutputDeviceEnumerator::Enumerate() comment to explain that.

-    for (const auto& entry : device_enumeration) {
+  if (device_enumeration.has_actual_devices) {
+    for (const auto& entry : device_enumeration.devices) {
       StreamDeviceInfo device_info(MEDIA_DEVICE_AUDIO_OUTPUT, entry.device_name,
                                    entry.unique_id);
       device_infos.push_back(device_info);
     }
   }
 
   const std::string log_message =
       "New device enumeration result:\n" +
       GetLogMessageString(MEDIA_DEVICE_AUDIO_OUTPUT, device_infos);
   SendMessageToNativeLog(log_message);
@@ skipping 1317 matching lines @@
     const std::string& device_guid,
     const std::string& raw_unique_id) {
   DCHECK(security_origin.is_valid());
   DCHECK(!raw_unique_id.empty());
   std::string guid_from_raw_device_id =
       GetHMACForMediaDeviceID(sc, security_origin, raw_unique_id);
   return guid_from_raw_device_id == device_guid;
 }
 
 }  // namespace content