Implement periodic bandwidth probing in application-limited region.

webrtc/modules/pacing/alr_detector.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 26 matching lines @@
 
 void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t now_ms) {
   RTC_DCHECK(estimated_bitrate_bps_);
 
   rate_.Update(bytes_sent, now_ms);
   rtc::Optional<uint32_t> rate = rate_.Rate(now_ms);
   if (!rate)
     return;
 
   int percentage = static_cast<int>(*rate) * 100 / estimated_bitrate_bps_;
-  if (percentage < kAlrStartUsagePercent && !application_limited_) {
-    application_limited_ = true;
-  } else if (percentage > kAlrEndUsagePercent && application_limited_) {
-    application_limited_ = false;
+  if (percentage < kAlrStartUsagePercent && !alr_started_time_ms_) {
+    alr_started_time_ms_ = rtc::Optional<int64_t>(now_ms);
+  } else if (percentage > kAlrEndUsagePercent && alr_started_time_ms_) {
+    alr_started_time_ms_ = rtc::Optional<int64_t>();
   }
 }
 
 void AlrDetector::SetEstimatedBitrate(int bitrate_bps) {
   RTC_DCHECK(bitrate_bps);
   estimated_bitrate_bps_ = bitrate_bps;
 }
 
-bool AlrDetector::InApplicationLimitedRegion() const {
-  return application_limited_;
+rtc::Optional<int64_t> AlrDetector::GetApplicationLimitedRegionStartTime()
+    const {
+  return alr_started_time_ms_;
 }
 
 }  // namespace webrtc