Dynamic resolution change for VP8 HW encode.

Off by default for now.

BUG=
R=glaznev@webrtc.org, stefan@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/45849004

Cr-Commit-Position: refs/heads/master@{#9045}

webrtc/modules/video_coding/utility/include/moving_average.h

@@ -0,0 +1,71 @@
+/*
+ *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_VIDEO_CODING_UTILITY_MOVING_AVERAGE_H_
+#define WEBRTC_MODULES_VIDEO_CODING_UTILITY_MOVING_AVERAGE_H_
+
+#include <list>
+
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+template<class T>
+class MovingAverage {
+ public:
+  MovingAverage();
+  void AddSample(T sample);
+  bool GetAverage(size_t num_samples, T* average);
+  void Reset();
+  int size();
+
+ private:
+  T sum_;
+  std::list<T> samples_;
+};
+
+template<class T>
+MovingAverage<T>::MovingAverage() : sum_(static_cast<T>(0)) {
+}
+
+template<class T>
+void MovingAverage<T>::AddSample(T sample) {
+  samples_.push_back(sample);
+  sum_ += sample;
+}
+
+template<class T>
+bool MovingAverage<T>::GetAverage(size_t num_samples, T* avg) {
+  if (num_samples > samples_.size())
+    return false;
+
+  // Remove old samples.
+  while (num_samples < samples_.size()) {
+    sum_ -= samples_.front();
+    samples_.pop_front();
+  }
+
+  *avg = sum_ / static_cast<T>(num_samples);
+  return true;
+}
+
+template<class T>
+void MovingAverage<T>::Reset() {
+  sum_ = static_cast<T>(0);
+  samples_.clear();
+}
+
+template<class T>
+int MovingAverage<T>::size() {
+  return samples_.size();
+}
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_VIDEO_CODING_MOVING_AVERAGE_SCALER_H_