Update constraints algorithm for video content capture.

content/renderer/media/media_stream_constraints_util_video_content.h

 // Copyright 2017 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_CONSTRAINTS_UTIL_VIDEO_CONTENT_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_CONSTRAINTS_UTIL_VIDEO_CONTENT_H_
 
 #include <string>
 
 #include "content/common/content_export.h"
 #include "content/renderer/media/media_stream_constraints_util.h"
 #include "third_party/webrtc/base/optional.h"
 
 namespace blink {
 class WebMediaConstraints;
 }
 
 namespace content {
 
 CONTENT_EXPORT extern const int kDefaultScreenCastWidth;
 CONTENT_EXPORT extern const int kDefaultScreenCastHeight;
+CONTENT_EXPORT extern const double kDefaultScreenCastAspectRatio;
 CONTENT_EXPORT extern const double kDefaultScreenCastFrameRate;
 CONTENT_EXPORT extern const int kMinScreenCastDimension;
 CONTENT_EXPORT extern const int kMaxScreenCastDimension;
 
 // This function performs source, source-settings and track-settings selection
 // for content video capture based on the given |constraints|.
 VideoCaptureSettings CONTENT_EXPORT SelectSettingsVideoContentCapture(
     const blink::WebMediaConstraints& constraints);
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_CONSTRAINTS_UTIL_VIDEO_CONTENT_H_