[Cast] Compute utilization metrics and add performance overlay.

media/cast/sender/sender_encoded_frame.h

+// Copyright 2015 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 MEDIA_CAST_SENDER_SENDER_ENCODED_FRAME_H_
+#define MEDIA_CAST_SENDER_SENDER_ENCODED_FRAME_H_
+
+#include "media/cast/net/cast_transport_config.h"
+
+namespace media {
+namespace cast {
+
+// Extends EncodedFrame with additional fields used within the sender-side of
+// the library.
+struct SenderEncodedFrame : public EncodedFrame {
+  SenderEncodedFrame();
+  ~SenderEncodedFrame() final;
+
+  // The amount of real-world time it took to encode the frame, divided by the
+  // maximum amount of time allowed.  Example: For the software VP8 encoder,
+  // this would be the elapsed encode time (according to the base::TimeTicks
+  // clock) divided by the VideoFrame's duration.
+  //
+  // Meaningful values are non-negative, with 0.0 [impossibly] representing 0%
+  // utilization, 1.0 representing 100% utilization, and values greater than 1.0
+  // indicating the encode time took longer than the media duration of the
+  // frame.  Negative values indicate the field was not computed.
+  double deadline_utilization;
+
+  // The amount of "lossiness" needed to encode the frame within the targeted
+  // bandwidth.  More-complex frame content and/or lower target encode bitrates
+  // will cause this value to rise.
+  //
+  // Meaningful values are non-negative, with 0.0 indicating the frame is very
+  // simple and/or the target encode bitrate is very large, 1.0 indicating the
+  // frame contains very complex content and/or the target encode bitrate is
+  // very small, and values greater than 1.0 indicating the encoder cannot
+  // encode the frame within the target bitrate (even at its lowest quality
+  // setting).  Negative values indicate the field was not computed.
+  double lossy_utilization;
+};
+
+}  // namespace cast
+}  // namespace media
+
+#endif  // MEDIA_CAST_SENDER_SENDER_ENCODED_FRAME_H_