Refactor how padding is calculated.

webrtc/call/bitrate_allocator.h

Index: webrtc/call/bitrate_allocator.h
diff --git a/webrtc/call/bitrate_allocator.h b/webrtc/call/bitrate_allocator.h
index bf26a6ae9bbc2d035f8dbd51eeab3b300348116c..983aae0e1e9fb0dc75fa0dcff958f3308481f3a8 100644
--- a/webrtc/call/bitrate_allocator.h
+++ b/webrtc/call/bitrate_allocator.h
@@ -31,6 +31,8 @@ class BitrateAllocatorObserver {
   virtual void OnBitrateUpdated(uint32_t bitrate_bps,
                                 uint8_t fraction_loss,
                                 int64_t rtt) = 0;
+
+ protected:
   virtual ~BitrateAllocatorObserver() {}
 };
 
@@ -39,14 +41,24 @@ class BitrateAllocatorObserver {
 // and push the result to the encoders via BitrateAllocatorObserver(s).
 class BitrateAllocator {
  public:
-  BitrateAllocator();
+  // Used to get notified when send stream limits such as the minimum send
+  // bitrate and max padding bitrate is changed.
+  class LimitObserver {
+   public:
+    virtual void OnAllocationLimitsChanged(
+        uint32_t min_send_bitrate_bps,
+        uint32_t max_padding_bitrate_bps) = 0;
+
+   protected:
+    virtual ~LimitObserver() {}
+  };
+
+  explicit BitrateAllocator(LimitObserver* limit_observer);
 
   // Allocate target_bitrate across the registered BitrateAllocatorObservers.
-  // Returns actual bitrate allocated (might be higher than target_bitrate if
-  // for instance EnforceMinBitrate() is enabled.
-  uint32_t OnNetworkChanged(uint32_t target_bitrate,
-                            uint8_t fraction_loss,
-                            int64_t rtt);
+  void OnNetworkChanged(uint32_t target_bitrate,
+                        uint8_t fraction_loss,
+                        int64_t rtt);
 
   // Set the start and max send bitrate used by the bandwidth management.
   //
@@ -64,6 +76,7 @@ class BitrateAllocator {
   int AddObserver(BitrateAllocatorObserver* observer,
                   uint32_t min_bitrate_bps,
                   uint32_t max_bitrate_bps,
+                  uint32_t pad_up_bitrate_bps,
                   bool enforce_min_bitrate);
 
   void RemoveObserver(BitrateAllocatorObserver* observer);
@@ -73,17 +86,24 @@ class BitrateAllocator {
     ObserverConfig(BitrateAllocatorObserver* observer,
                    uint32_t min_bitrate_bps,
                    uint32_t max_bitrate_bps,
+                   uint32_t pad_up_bitrate_bps,
                    bool enforce_min_bitrate)
         : observer(observer),
           min_bitrate_bps(min_bitrate_bps),
           max_bitrate_bps(max_bitrate_bps),
+          pad_up_bitrate_bps(pad_up_bitrate_bps),
           enforce_min_bitrate(enforce_min_bitrate) {}
     BitrateAllocatorObserver* const observer;
     uint32_t min_bitrate_bps;
     uint32_t max_bitrate_bps;
+    uint32_t pad_up_bitrate_bps;
     bool enforce_min_bitrate;
   };
 
+  // Calculates the minimum requested send bitrate and max padding bitrate and
+  // calls LimitObserver::OnAllocationLimitsChanged.
+  void UpdateAllocationLimits();
+
   // This method controls the behavior when the available bitrate is lower than
   // the minimum bitrate, or the sum of minimum bitrates.
   // When true, the bitrate will never be set lower than the minimum bitrate(s).
@@ -110,6 +130,8 @@ class BitrateAllocator {
   ObserverAllocation LowRateAllocation(uint32_t bitrate)
       EXCLUSIVE_LOCKS_REQUIRED(crit_sect_);
 
+  LimitObserver* const limit_observer_;
+
   rtc::CriticalSection crit_sect_;
   // Stored in a list to keep track of the insertion order.
   ObserverConfigList bitrate_observer_configs_ GUARDED_BY(crit_sect_);