Switch to PacketNumberQueue interval iteration and avoid allocations in new ACK frame generation. G…

net/quic/quic_protocol.h

Index: net/quic/quic_protocol.h
diff --git a/net/quic/quic_protocol.h b/net/quic/quic_protocol.h
index d5e606301aa9e2a6c55e57c177870781e3a1bf9a..2b57eafc995b8f743022ad53f3c7506f2e4c4b68 100644
--- a/net/quic/quic_protocol.h
+++ b/net/quic/quic_protocol.h
@@ -894,6 +894,9 @@ struct NET_EXPORT_PRIVATE QuicStopWaitingFrame {
 // larger new packet numbers are added, with the occasional random access.
 class NET_EXPORT_PRIVATE PacketNumberQueue {
  public:
+  using const_interval_iterator = IntervalSet<QuicPacketNumber>::const_iterator;
+  using const_reverse_interval_iterator =
+      IntervalSet<QuicPacketNumber>::const_reverse_iterator;
   // TODO(jdorfman): remove const_iterator and change the callers to iterate
   // over the intervals.
   class NET_EXPORT_PRIVATE const_iterator
@@ -993,6 +996,12 @@ class NET_EXPORT_PRIVATE PacketNumberQueue {
       std::ostream& os,
       const PacketNumberQueue& q);
 
+  // Returns iterators over the packet number intervals.
+  const_interval_iterator begin_intervals() const;
+  const_interval_iterator end_intervals() const;
+  const_reverse_interval_iterator rbegin_intervals() const;
+  const_reverse_interval_iterator rend_intervals() const;
+
  private:
   IntervalSet<QuicPacketNumber> packet_number_intervals_;
 };