Change QUIC's pacing sender to send at 1.25x the estimated bandwidth

net/quic/congestion_control/send_algorithm_interface.h

Index: net/quic/congestion_control/send_algorithm_interface.h
diff --git a/net/quic/congestion_control/send_algorithm_interface.h b/net/quic/congestion_control/send_algorithm_interface.h
index 080ff37c8613d6785e25478590fe7c4eb88b75c3..9633ecd86cd6a5bafd2981a74e126e009008f8fc 100644
--- a/net/quic/congestion_control/send_algorithm_interface.h
+++ b/net/quic/congestion_control/send_algorithm_interface.h
@@ -93,6 +93,10 @@ class NET_EXPORT_PRIVATE SendAlgorithmInterface {
   // window and will return 0.
   virtual QuicByteCount GetCongestionWindow() const = 0;
 
+  // Whether the send algorithm is currently in slow start.  When true, the
+  // BandwidthEstimate is expected to be too low.
+  virtual bool InSlowStart() const = 0;
+
   // Returns the size of the slow start congestion window in bytes,
   // aka ssthresh.  Some send algorithms do not define a slow start
   // threshold and will return 0.