Track the number of "early" frames received in a QUIC stream.

net/quic/quic_stream_sequencer.cc

Index: net/quic/quic_stream_sequencer.cc
diff --git a/net/quic/quic_stream_sequencer.cc b/net/quic/quic_stream_sequencer.cc
index ceeaa943a4898c3c2b08f85f8ba9fa141cb1b0fe..7a9ae0dba981695af198077e5487e259851b0d87 100644
--- a/net/quic/quic_stream_sequencer.cc
+++ b/net/quic/quic_stream_sequencer.cc
@@ -25,7 +25,8 @@ QuicStreamSequencer::QuicStreamSequencer(ReliableQuicStream* quic_stream)
       blocked_(false),
       num_bytes_buffered_(0),
       num_frames_received_(0),
-      num_duplicate_frames_received_(0) {
+      num_duplicate_frames_received_(0),
+      num_early_frames_received_(0) {
 }
 
 QuicStreamSequencer::~QuicStreamSequencer() {
@@ -64,6 +65,10 @@ void QuicStreamSequencer::OnStreamFrame(const QuicStreamFrame& frame) {
   IOVector data;
   data.AppendIovec(frame.data.iovec(), frame.data.Size());
 
+  if (byte_offset > num_bytes_consumed_) {
+    ++num_early_frames_received_;
+  }
+
   // If the frame has arrived in-order then we can process it immediately, only
   // buffering if the stream is unable to process it.
   if (!blocked_ && byte_offset == num_bytes_consumed_) {