Add histogram stats for number of cpu/quality adapt changes per minute for sent video streams:

webrtc/video/vie_encoder.cc

 /*
  *  Copyright (c) 2012 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 523 matching lines @@
   RTC_DCHECK_RUN_ON(&encoder_queue_);
   const auto scaling_settings = settings_.encoder->GetScalingSettings();
   const bool degradation_preference_allows_scaling =
       degradation_preference_ == DegradationPreference::kMaintainFramerate ||
       degradation_preference_ == DegradationPreference::kBalanced;
   const bool quality_scaling_allowed =
       degradation_preference_allows_scaling && scaling_settings.enabled;
 
   const std::vector<int>& scale_counters = GetScaleCounters();
   stats_proxy_->SetCpuScalingStats(
-      degradation_preference_allows_scaling ? scale_counters[kCpu] > 0 : false);
+      degradation_preference_allows_scaling ? scale_counters[kCpu] : -1);
   stats_proxy_->SetQualityScalingStats(
       quality_scaling_allowed ? scale_counters[kQuality] : -1);
 
   if (quality_scaling_allowed) {
     // Abort if quality scaler has already been configured.
     if (quality_scaler_.get() != nullptr)
       return;
     // Drop frames and scale down until desired quality is achieved.
     if (scaling_settings.thresholds) {
       quality_scaler_.reset(
@@ skipping 416 matching lines @@
 void ViEEncoder::IncrementScaleCounter(int reason, int delta) {
   // Get the counters and validate. This may also lazily initialize the state.
   const std::vector<int>& counter = GetScaleCounters();
   if (delta < 0) {
     RTC_DCHECK_GE(counter[reason], delta);
   }
   scale_counters_[degradation_preference_][reason] += delta;
 }
 
 }  // namespace webrtc