Reimplemeted "Test and fix for huge bwe drop after alr state"

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 93752cf751395d99db60e146ef87f4b0558e4dcb..226be4823b0e2e3f00b3dfff5205b70ad0c6205e 100644
--- a/webrtc/modules/pacing/alr_detector.cc
+++ b/webrtc/modules/pacing/alr_detector.cc
@@ -103,4 +103,19 @@ AlrDetector::ParseAlrSettingsFromFieldTrial() {
   return ret;
 }
 
+AlrState::Change AlrState::ChangeWhenAlrStartTimeIs(
+    rtc::Optional<int64_t> alr_start_time_ms) {
+  AlrState::Change state_change = AlrState::Change::kNoChange;
+
+  if (was_in_alr_ && !alr_start_time_ms)
+    state_change = AlrState::Change::kEnded;
+
+  if (!was_in_alr_ && alr_start_time_ms)
+    state_change = AlrState::Change::kStarted;
+
+  was_in_alr_ = alr_start_time_ms.has_value();
+
+  return state_change;
+}
+
 }  // namespace webrtc