Add algorithm for processing constraints 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 "media/capture/video_capture_types.h"
+#include "third_party/webrtc/base/optional.h"
+
+namespace blink {
+class WebMediaConstraints;
+}
+
+namespace content {
+
+class CONTENT_EXPORT VideoContentCaptureSourceSelectionResult {
+ public:
+  // Creates a result without value and with the given |failed_constraint_name|.
+  // Does not take ownership of |failed_constraint_name|, so it must be null or
+  // point to a string that remains accessible.
+  explicit VideoContentCaptureSourceSelectionResult(
+      const char* failed_constraint_name);
+
+  // Creates a result with the given values. |device_id| is moved to an internal
+  // field.
+  VideoContentCaptureSourceSelectionResult(
+      std::string device_id,
+      const rtc::Optional<bool>& noise_reduction,
+      media::VideoCaptureParams capture_params);
+
+  VideoContentCaptureSourceSelectionResult(
+      const VideoContentCaptureSourceSelectionResult& other);
+  VideoContentCaptureSourceSelectionResult& operator=(
+      const VideoContentCaptureSourceSelectionResult& other);
+  VideoContentCaptureSourceSelectionResult(
+      VideoContentCaptureSourceSelectionResult&& other);
+  VideoContentCaptureSourceSelectionResult& operator=(
+      VideoContentCaptureSourceSelectionResult&& other);
+  ~VideoContentCaptureSourceSelectionResult();
+
+  bool HasValue() const { return failed_constraint_name_ == nullptr; }
+
+  // Accessors.
+  const char* failed_constraint_name() const { return failed_constraint_name_; }
+  const std::string& device_id() const { return device_id_; }
+  const rtc::Optional<bool>& noise_reduction() const {
+    return noise_reduction_;
+  }
+  media::VideoCaptureParams capture_params() const { return capture_params_; }
+
+  // Convenience accessors for fields embedded in the |capture_params_| field.
+  int Height() const;
+  int Width() const;
+  float FrameRate() const;
+  media::ResolutionChangePolicy ResolutionChangePolicy() const;
+
+ private:
+  const char* failed_constraint_name_;
+  std::string device_id_;
+  rtc::Optional<bool> noise_reduction_;
+  media::VideoCaptureParams capture_params_;
+};
+
+// This function performs source and source-settings selection for content
+// video capture based on the given |constraints|.
+VideoContentCaptureSourceSelectionResult CONTENT_EXPORT
+SelectVideoContentCaptureSourceSettings(
+    const blink::WebMediaConstraints& constraints);
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_CONSTRAINTS_UTIL_VIDEO_CONTENT_H_