relnote: Measure HOL blocking in QUIC headers stream. Flag protected by quic_measure_headers_hol_bl…

net/quic/quic_stream_sequencer.h

Index: net/quic/quic_stream_sequencer.h
diff --git a/net/quic/quic_stream_sequencer.h b/net/quic/quic_stream_sequencer.h
index a1bdd327c644b9f07450b6b034a73eb4abb3782b..c73ed47ec9e336ea6f7d8a352e0a4d03a6aab0fb 100644
--- a/net/quic/quic_stream_sequencer.h
+++ b/net/quic/quic_stream_sequencer.h
@@ -18,6 +18,7 @@ namespace test {
 class QuicStreamSequencerPeer;
 }  // namespace test
 
+class QuicClock;
 class QuicSession;
 class ReliableQuicStream;
 
@@ -25,7 +26,7 @@ class ReliableQuicStream;
 // up to the next layer.
 class NET_EXPORT_PRIVATE QuicStreamSequencer {
  public:
-  explicit QuicStreamSequencer(ReliableQuicStream* quic_stream);
+  QuicStreamSequencer(ReliableQuicStream* quic_stream, const QuicClock* clock);
   virtual ~QuicStreamSequencer();
 
   // If the frame is the next one we need in order to process in-order data,
@@ -42,6 +43,12 @@ class NET_EXPORT_PRIVATE QuicStreamSequencer {
   // number of iovs used.  Non-destructive of the underlying data.
   int GetReadableRegions(iovec* iov, size_t iov_len) const;
 
+  // Fills in one iovec with the next readable region.  |timestamp| is
+  // data arrived at the sequencer, and is used for measuring head of
+  // line blocking (HOL).  Returns false if there is no readable
+  // region available.
+  bool GetReadableRegion(iovec* iov, QuicTime* timestamp) const;
+
   // Copies the data into the iov_len buffers provided.  Returns the number of
   // bytes read.  Any buffered data no longer in use will be released.
   // TODO(rch): remove this method and instead implement it as a helper method
@@ -121,6 +128,9 @@ class NET_EXPORT_PRIVATE QuicStreamSequencer {
   // received.
   int num_early_frames_received_;
 
+  // Not owned.
+  const QuicClock* clock_;
+
   DISALLOW_COPY_AND_ASSIGN(QuicStreamSequencer);
 };