Implement periodic bandwidth probing in application-limited region.

webrtc/modules/pacing/alr_detector.cc

Index: webrtc/modules/pacing/alr_detector.cc
diff --git a/webrtc/modules/pacing/alr_detector.cc b/webrtc/modules/pacing/alr_detector.cc
index d0c5618b9c0f73217386f14058001bde9cf31842..d92ec45f64fc0c89b4cb7bbd02c3051d1bce2b5f 100644
--- a/webrtc/modules/pacing/alr_detector.cc
+++ b/webrtc/modules/pacing/alr_detector.cc
@@ -44,10 +44,10 @@ void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t now_ms) {
     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_ = now_ms;
+  } else if (percentage > kAlrEndUsagePercent && alr_started_time_ms_) {
+    alr_started_time_ms_ = 0;
   }
 }
 
@@ -56,8 +56,8 @@ void AlrDetector::SetEstimatedBitrate(int bitrate_bps) {
   estimated_bitrate_bps_ = bitrate_bps;
 }
 
-bool AlrDetector::InApplicationLimitedRegion() {
-  return application_limited_;
+int64_t AlrDetector::GetApplicationLimitedRegionStartTime() const {
+  return alr_started_time_ms_;
 }
 
 }  // namespace webrtc