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

webrtc/modules/pacing/alr_detector.h

Index: webrtc/modules/pacing/alr_detector.h
diff --git a/webrtc/modules/pacing/alr_detector.h b/webrtc/modules/pacing/alr_detector.h
index 11eeceaa988a65bdff24308e294902f1eaa23567..0a58c7fbad76f20aee1550b35c0322fbc707142a 100644
--- a/webrtc/modules/pacing/alr_detector.h
+++ b/webrtc/modules/pacing/alr_detector.h
@@ -27,7 +27,6 @@ namespace webrtc {
 // AlrDetector provides a signal that can be utilized to adjust
 // estimate bandwidth.
 // Note: This class is not thread-safe.
-
 class AlrDetector {
  public:
   AlrDetector();
@@ -57,8 +56,8 @@ class AlrDetector {
   // kAlrEndUsagePercent. NOTE: This is intentionally conservative at the moment
   // until BW adjustments of application limited region is fine tuned.
   static constexpr int kDefaultAlrBandwidthUsagePercent = 65;
-  static constexpr int kDefaultAlrStartBudgetLevelPercent = 20;
-  static constexpr int kDefaultAlrStopBudgetLevelPercent = -20;
+  static constexpr int kDefaultAlrStartBudgetLevelPercent = 80;

[terelius, 2017/07/13 10:46:01]

These numbers have changed a lot. How certain are we that that the new values
are correct? Do the numbers matter or only the difference?

[tschumi, 2017/07/13 11:54:35]

The detector was to slow in reporting the leafing alr. So we already overused
before alr left was reported. 

So i changed the thresholds in way that it takes more time till we report "in
alr" and less time til we report "left alr".  

Is hard to tell if the numbers are correct.

+  static constexpr int kDefaultAlrStopBudgetLevelPercent = 50;
   static const char* kScreenshareProbingBweExperimentName;
 
   void UpdateBudgetWithElapsedTime(int64_t delta_time_ms);
@@ -70,9 +69,24 @@ class AlrDetector {
   int alr_stop_budget_level_percent_;
 
   IntervalBudget alr_budget_;
+  int estimated_bitrate_bps_;
   rtc::Optional<int64_t> alr_started_time_ms_;
 };
 
+class AlrState {
+ public:
+  enum class Change {
+    kEnded,
+    kStarted,
+    kNoChange,
+  };
+
+  Change ChangeWhenAlrStartTimeIs(rtc::Optional<int64_t> alr_start_time_ms);
+
+ private:
+  bool was_in_alr_;
+};
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_PACING_ALR_DETECTOR_H_