Fix the semantics of QuicFecGroup::ProtectsPacketsBefore into IsWaitingForPacketBefore. Certain ed…

net/quic/quic_fec_group.cc

Index: net/quic/quic_fec_group.cc
diff --git a/net/quic/quic_fec_group.cc b/net/quic/quic_fec_group.cc
index 51194d1212378247f8f40551c6e01c12564775a5..c9aaa812c1414ababe56416733f92b6c07433319 100644
--- a/net/quic/quic_fec_group.cc
+++ b/net/quic/quic_fec_group.cc
@@ -118,13 +118,31 @@ size_t QuicFecGroup::Revive(QuicPacketHeader* header,
   return payload_parity_len_;
 }
 
-bool QuicFecGroup::ProtectsPacketsBefore(QuicPacketNumber num) const {
-  if (has_received_fec_packet()) {
-    return max_protected_packet_ < num;
+bool QuicFecGroup::IsWaitingForPacketBefore(QuicPacketNumber num) const {
+  // Entire range is larger than the threshold.
+  if (min_protected_packet_ >= num) {
+    return false;
+  }
+
+  // Entire range is smaller than the threshold.
+  if (received_packets_.size() > 0 ? *received_packets_.rbegin() + 1 < num
+                                   : min_protected_packet_ < num) {
+    return true;
+  }
+
+  // Range spans the threshold so look for a missing packet below the threshold.
+  QuicPacketNumber target = min_protected_packet_;
+  for (QuicPacketNumber packet : received_packets_) {
+    if (target++ != packet) {
+      return true;
+    }
+    if (target >= num) {
+      return false;
+    }
   }
-  // Since we might not yet have received the FEC packet, we must check
-  // the packets we have received.
-  return *received_packets_.begin() < num;
+
+  // No missing packets below the threshold.
+  return false;
 }
 
 bool QuicFecGroup::UpdateParity(StringPiece payload) {