Revert of Remove SendPacer from ViEEncoder

webrtc/call/bitrate_allocator.cc

Index: webrtc/call/bitrate_allocator.cc
diff --git a/webrtc/call/bitrate_allocator.cc b/webrtc/call/bitrate_allocator.cc
index 4c8d2a0c441bb20f41d7dd7ac30eb4a2110a85d2..097378f02a17b9728581d955c83dfe5860b31681 100644
--- a/webrtc/call/bitrate_allocator.cc
+++ b/webrtc/call/bitrate_allocator.cc
@@ -54,9 +54,7 @@
   uint32_t sum_min_bitrates = 0;
   for (const auto& observer : bitrate_observers_)
     sum_min_bitrates += observer.second.min_bitrate;
-  if (last_bitrate_bps_ == 0)
-    return ZeroRateAllocation();
-  else if (last_bitrate_bps_ <= sum_min_bitrates)
+  if (last_bitrate_bps_ <= sum_min_bitrates)
     return LowRateAllocation(last_bitrate_bps_);
   else
     return NormalRateAllocation(last_bitrate_bps_, sum_min_bitrates);
@@ -103,6 +101,18 @@
   if (it != bitrate_observers_.end()) {
     bitrate_observers_.erase(it);
     bitrate_observers_modified_ = true;
+  }
+}
+
+void BitrateAllocator::GetMinMaxBitrateSumBps(int* min_bitrate_sum_bps,
+                                              int* max_bitrate_sum_bps) const {
+  *min_bitrate_sum_bps = 0;
+  *max_bitrate_sum_bps = 0;
+
+  rtc::CritScope lock(&crit_sect_);
+  for (const auto& observer : bitrate_observers_) {
+    *min_bitrate_sum_bps += observer.second.min_bitrate;
+    *max_bitrate_sum_bps += observer.second.max_bitrate;
   }
 }
 
@@ -160,14 +170,6 @@
   return allocation;
 }
 
-BitrateAllocator::ObserverBitrateMap BitrateAllocator::ZeroRateAllocation() {
-  ObserverBitrateMap allocation;
-  // Zero bitrate to all observers.
-  for (const auto& observer : bitrate_observers_)
-    allocation[observer.first] = 0;
-  return allocation;
-}
-
 BitrateAllocator::ObserverBitrateMap BitrateAllocator::LowRateAllocation(
     uint32_t bitrate) {
   ObserverBitrateMap allocation;