Add UMA stats to bad call detection.

webrtc/video/quality_threshold.cc

 /*
  *  Copyright (c) 2016 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.
  */
 
@@ skipping 10 matching lines @@
                                    int max_measurements)
     : buffer_(new int[max_measurements]),
       max_measurements_(max_measurements),
       fraction_(fraction),
       low_threshold_(low_threshold),
       high_threshold_(high_threshold),
       until_full_(max_measurements),
       next_index_(0),
       sum_(0),
       count_low_(0),
-      count_high_(0) {
+      count_high_(0),
+      num_high_states_(0),
+      num_certain_states_(0) {
   RTC_CHECK_GT(fraction, 0.5f);
   RTC_CHECK_GT(max_measurements, 1);
   RTC_CHECK_LT(low_threshold, high_threshold);
 }
 
 void QualityThreshold::AddMeasurement(int measurement) {
   int prev_val = until_full_ > 0 ? 0 : buffer_[next_index_];
   buffer_[next_index_] = measurement;
   next_index_ = (next_index_ + 1) % max_measurements_;
 
@@ skipping 15 matching lines @@
 
   float sufficient_majority = fraction_ * max_measurements_;
   if (count_high_ >= sufficient_majority) {
     is_high_ = rtc::Optional<bool>(true);
   } else if (count_low_ >= sufficient_majority) {
     is_high_ = rtc::Optional<bool>(false);
   }
 
   if (until_full_ > 0)
     --until_full_;
+
+  if (is_high_) {
+    if (*is_high_)
+      ++num_high_states_;
+    ++num_certain_states_;
+  }
 }
 
 rtc::Optional<bool> QualityThreshold::IsHigh() const {
   return is_high_;
 }
 
 rtc::Optional<double> QualityThreshold::CalculateVariance() const {
   if (until_full_ > 0) {
     return rtc::Optional<double>();
   }
 
   double variance = 0;
   double mean = static_cast<double>(sum_) / max_measurements_;
   for (int i = 0; i < max_measurements_; ++i) {
     variance += (buffer_[i] - mean) * (buffer_[i] - mean);
   }
   return rtc::Optional<double>(variance / (max_measurements_ - 1));
 }
 
+rtc::Optional<double> QualityThreshold::FractionHigh(
+    int min_required_samples) const {
+  RTC_DCHECK_GT(min_required_samples, 0);
+  if (num_certain_states_ < min_required_samples)
+    return rtc::Optional<double>();
+
+  return rtc::Optional<double>(static_cast<double>(num_high_states_) /
+                               num_certain_states_);
+}
+
 }  // namespace webrtc