Implement GetUserMedia device ID constraint processing in the renderer.

content/common/media/media_stream_options.h

 // 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.
 
 #ifndef CONTENT_COMMON_MEDIA_MEDIA_STREAM_OPTIONS_H_
 #define CONTENT_COMMON_MEDIA_MEDIA_STREAM_OPTIONS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 15 matching lines @@
   TrackControls();
   explicit TrackControls(bool request);
   explicit TrackControls(const TrackControls& other);
   ~TrackControls();
   bool requested;
 
   // Source. This is "tab", "screen", "desktop", "system", or blank.
   // Consider replacing with MediaStreamType enum variables.
   std::string stream_source;  // audio.kMediaStreamSource
 
-  // Device ID requests.
-  // The first set represents required devices - either grab one or fail.
-  // The second set represents optional devices - if we can't get one of
-  // these, we will grab the default device (if possible).
-  // The constraint names are "sourceId" and "chromeMediaSourceId".
-  std::vector<std::string> device_ids;
-  std::vector<std::string> alternate_device_ids;
+  // Empty string represents the default device.
+  // Nonempty string represents a specific device.

[hta - Chromium, 2016/11/30 18:51:42]

Nit, English: "An empty string represents the default device. A nonempty string
represents a specific device."

[Guido Urdaneta, 2016/12/01 10:28:53]

Done.

+  std::string device_id;
 };
 
 // StreamControls describes what is sent to the browser process
 // to the renderer process in order to control the opening of a device

[hta - Chromium, 2016/11/30 18:51:43]

Fix the grammar of "to the browser proces to the renderer process", please - I
think the second "to" should be "from".

[Guido Urdaneta, 2016/12/01 10:28:53]

Done.

 // pair. This may result in opening one audio and/or one video device.
 // This has to be a struct with public members in order to allow it to
 // be sent in the IPC of media_stream_messages.h
 struct CONTENT_EXPORT StreamControls {
  public:
   StreamControls();
   StreamControls(bool request_audio, bool request_video);
   ~StreamControls();
   TrackControls audio;
   TrackControls video;
@@ skipping 24 matching lines @@
 
   // Id for this capture session. Unique for all sessions of the same type.
   int session_id;
 };
 
 typedef std::vector<StreamDeviceInfo> StreamDeviceInfoArray;
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_MEDIA_MEDIA_STREAM_OPTIONS_H_