Land Recent QUIC changes.

net/quic/quic_packet_generator.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Responsible for generating packets on behalf of a QuicConnection.
 // Packets are serialized just-in-time.  Control frames are queued.
 // Ack and Feedback frames will be requested from the Connection
 // just-in-time.  When a packet needs to be sent, the Generator
 // will serialize a packet and pass it to QuicConnection::SendOrQueuePacket()
 //
@@ skipping 90 matching lines @@
 
   bool HasQueuedFrames() const;
 
   void set_debug_delegate(DebugDelegateInterface* debug_delegate) {
     debug_delegate_ = debug_delegate;
   }
 
  private:
   void SendQueuedFrames();
 
+  // Test to see if we have pending ack, feedback, or control frames.
   bool HasPendingFrames() const;
+  // Test to see if the addition of a pending frame (which might be
+  // retransmittable) would still allow the resulting packet to be sent now.
+  bool CanSendWithNextPendingFrameAddition() const;
+  // Add exactly one pending frame, preferring ack over feedback over control
+  // frames.
   bool AddNextPendingFrame();
 
   bool AddFrame(const QuicFrame& frame);
   void SerializeAndSendPacket();
 
   DelegateInterface* delegate_;
   DebugDelegateInterface* debug_delegate_;
 
   QuicPacketCreator* packet_creator_;
   QuicFrames queued_control_frames_;
   bool should_flush_;
+  // Flags to indicate the need for just-in-time construction of a frame.
   bool should_send_ack_;
+  bool should_send_feedback_;
+  // If we put a non-retransmittable frame (namley ack or feedback frame) in
+  // this packet, then we have to hold a reference to it until we flush (and
+  // serialize it). Retransmittable frames are referenced elsewhere so that they
+  // can later be (optionally) retransmitted.
   scoped_ptr<QuicAckFrame> pending_ack_frame_;
   scoped_ptr<QuicCongestionFeedbackFrame> pending_feedback_frame_;
-  bool should_send_feedback_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicPacketGenerator);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_PACKET_GENERATOR_H_