Add two new histogram to tracking QUIC packet reordering:

* Net.QuicSession.MaxReordering
* Net.QuicSession.MaxReorderingTime
* Net.QuicSession.MaxReorderingTimeLongRtt

Review URL: https://codereview.chromium.org/298893010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272631 0039d316-1c4b-4281-b951-d872f2087c98

net/quic/quic_client_session.cc

@@ -243,6 +243,17 @@ QuicClientSession::~QuicClientSession() {
                                   round_trip_handshakes, 0, 3, 4);
     }
   }
+  const QuicConnectionStats stats = connection()->GetStats();
+  uint64 reordering =
+      GG_UINT64_C(100) * stats.max_time_reordering_us / stats.min_rtt_us;
+    UMA_HISTOGRAM_CUSTOM_COUNTS("Net.QuicSession.MaxReorderingTime",
+                                reordering, 0, 100, 50);
+  if (stats.min_rtt_us > 100) {
+    UMA_HISTOGRAM_CUSTOM_COUNTS("Net.QuicSession.MaxReorderingTimeLongRtt",
+                                reordering, 0, 100, 50);
+  }
+  UMA_HISTOGRAM_COUNTS("Net.QuicSession.MaxReordering",
+                       stats.max_sequence_reordering);
 }
 
 void QuicClientSession::OnStreamFrames(

tools/metrics/histograms/histograms.xml

@@ -13581,6 +13581,28 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicSession.MaxReordering">
+  <owner>rch@chromium.org</owner>
+  <summary>
+    The maximum packet sequence number reordering observed by a QUIC connection.
+  </summary>
+</histogram>
+
+<histogram name="Net.QuicSession.MaxReorderingTime" units="percent">
+  <owner>rch@chromium.org</owner>
+  <summary>
+    The ratio of the maximum reordering time of a QUIC packet to the min rtt.
+  </summary>
+</histogram>
+
+<histogram name="Net.QuicSession.MaxReorderingTimeLongRtt" units="percent">
+  <owner>rch@chromium.org</owner>
+  <summary>
+    The ratio of the maximum reordering time of a QUIC packet to the min rtt,
+    only for those sessions with a min rtt larger than 100 ms.
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicSession.NumOpenStreams">
   <owner>rch@chromium.org</owner>
   <summary>