QUIC - Added a histogram to track number of times session_ is null when

net/quic/quic_http_stream.cc

 // 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.
 
 #include "net/quic/quic_http_stream.h"
 
 #include "base/callback_helpers.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringprintf.h"
@@ skipping 593 matching lines @@
         NOTREACHED() << "next_state_: " << next_state_;
         break;
     }
   } while (next_state_ != STATE_NONE && next_state_ != STATE_OPEN &&
            rv != ERR_IO_PENDING);
 
   return rv;
 }
 
 int QuicHttpStream::DoStreamRequest() {
-  if (session_.get() == nullptr) {
-    // TODO(rtenneti) Bug: b/28676259 - a temporary fix until we find out why
-    // |session_| could be a nullptr.
+  // TODO(rtenneti) Bug: b/28676259 - a temporary fix until we find out why
+  // |session_| could be a nullptr. Delete |null_session| check and histogram if
+  // session is never a nullptr.
+  bool null_session = session_ == nullptr;
+  if (null_session) {
+    UMA_HISTOGRAM_BOOLEAN("Net.QuicHttpStream::DoStreamRequest.IsNullSession",
+                          null_session);
     return was_handshake_confirmed_ ? ERR_CONNECTION_CLOSED
                                     : ERR_QUIC_HANDSHAKE_FAILED;
   }
   int rv = stream_request_.StartRequest(
       session_, &stream_,
       base::Bind(&QuicHttpStream::OnStreamReady, weak_factory_.GetWeakPtr()));
   if (rv == OK) {
     stream_->SetDelegate(this);
     if (request_info_->load_flags & LOAD_DISABLE_CONNECTION_MIGRATION) {
       stream_->DisableConnectionMigration();
@@ skipping 181 matching lines @@
   closed_stream_sent_bytes_ = stream_->stream_bytes_written();
   stream_ = nullptr;
 
   // If |request_body_stream_| is non-NULL, Reset it, to abort any in progress
   // read.
   if (request_body_stream_)
     request_body_stream_->Reset();
 }
 
 }  // namespace net