Add utility set classes to support getUserMedia constraint proccessing.

content/renderer/media/media_stream_video_source.h

 // Copyright 2014 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_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 39 matching lines @@
   enum {
     // Default resolution. If no constraints are specified and the delegate
     // support it, this is the resolution that will be used.
     kDefaultWidth = 640,
     kDefaultHeight = 480,
 
     kDefaultFrameRate = 30,
     kUnknownFrameRate = 0,
   };
 
+  static constexpr double kDefaultAspectRatio =
+      static_cast<double>(kDefaultWidth) / static_cast<double>(kDefaultHeight);
+
   MediaStreamVideoSource();
   ~MediaStreamVideoSource() override;
 
   // Returns the MediaStreamVideoSource object owned by |source|.
   static MediaStreamVideoSource* GetVideoSource(
       const blink::WebMediaStreamSource& source);
 
   // Puts |track| in the registered tracks list.
   void AddTrack(MediaStreamVideoTrack* track,
                 const VideoCaptureDeliverFrameCB& frame_callback,
@@ skipping 133 matching lines @@
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<MediaStreamVideoSource> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamVideoSource);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_