Add histogram to record stream states when QUIC connection is closed due to idle timeout.

Bug: b/167434069
Change-Id: I57d5caef848498563e7932114cd880204b73c975
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391736Reviewed-by: David Schinazi <dschinazi@chromium.org>
Commit-Queue: David Schinazi <dschinazi@chromium.org>
Auto-Submit: Renjie Tang <renjietang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804346}

net/quic/quic_chromium_client_session.cc

@@ -1700,6 +1700,23 @@ void QuicChromiumClientSession::OnConnectionClosed(
   const quic::QuicErrorCode error = frame.quic_error_code;
   const std::string& error_details = frame.error_details;
 
+  if (source == quic::ConnectionCloseSource::FROM_SELF &&
+      error == quic::QUIC_NETWORK_IDLE_TIMEOUT && ShouldKeepConnectionAlive()) {
+    quic::QuicStreamCount streams_waiting_to_write = 0;
+    PerformActionOnActiveStreams(
+        [&streams_waiting_to_write](quic::QuicStream* stream) {
+          if (stream->HasBufferedData())
+            ++streams_waiting_to_write;
+          return true;
+        });
+
+    UMA_HISTOGRAM_COUNTS_100(
+        "Net.QuicSession.NumStreamsWaitingToWriteOnIdleTimeout",
+        streams_waiting_to_write);
+    UMA_HISTOGRAM_COUNTS_100("Net.QuicSession.NumActiveStreamsOnIdleTimeout",
+                             GetNumActiveStreams());
+  }
+
   if (source == quic::ConnectionCloseSource::FROM_PEER) {
     if (error == quic::QUIC_PUBLIC_RESET) {
       // is_from_google_server will be true if the received EPID is

tools/metrics/histograms/histograms.xml

@@ -103129,6 +103129,16 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicSession.NumActiveStreamsOnIdleTimeout" units="streams"
+    expires_after="2021-05-11">
+  <owner>renjietang@chromium.org</owner>
+  <owner>src/net/quic/OWNERS</owner>
+  <summary>
+    The number of active streams when idle timeout is detected and connection is
+    being closed.
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicSession.NumMigrationsExercisedBeforePublicReset"
     units="migrations" expires_after="2021-05-11">
   <owner>zhongyi@chromium.org</owner>
@@ -103194,6 +103204,16 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicSession.NumStreamsWaitingToWriteOnIdleTimeout"
+    units="streams" expires_after="2021-05-11">
+  <owner>renjietang@chromium.org</owner>
+  <owner>src/net/quic/OWNERS</owner>
+  <summary>
+    The number of streams waiting to write when idle timeout is detected and
+    connection is being closed.
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicSession.NumTotalStreams" units="units"
     expires_after="2021-05-11">
   <owner>dschinazi@chromium.org</owner>