Add one more histogram to log how many Request are still pending when

net/http/http_stream_factory_impl.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/http/http_stream_factory_impl.h"
 
 #include <string>
 #include <tuple>
 
 #include "base/logging.h"
@@ skipping 354 matching lines @@
       job_controller_set_.size() <= last_logged_job_controller_count_) {
     return;
   }
   last_logged_job_controller_count_ = job_controller_set_.size();
 
   UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfJobController",
                           job_controller_set_.size());
 
   int alt_job_count = 0;
   int main_job_count = 0;
+  int pending_request_count = 0;
   int preconnect_controller_count = 0;
   for (const auto& job_controller : job_controller_set_) {
     DCHECK(job_controller->HasPendingAltJob() ||
            job_controller->HasPendingMainJob());
     // For a preconnect controller, it should have exactly the main job.
     if (job_controller->is_preconnect()) {
       preconnect_controller_count++;
       continue;
     }
     // For non-preconnects.
+    if (job_controller->HasPendingRequest())
+      pending_request_count++;
     if (job_controller->HasPendingAltJob())
       alt_job_count++;
     if (job_controller->HasPendingMainJob())
       main_job_count++;
   }
   UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfPreconnect",
                           preconnect_controller_count);
   UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfNonPreconnectAltJob",
                           alt_job_count);
   UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfNonPreconnectMainJob",
                           main_job_count);
+  UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfPendingRequest",

[Steven Holte, 2017/04/14 22:46:44]

It seems like 1M is much bigger than range of actual values you are recording in
this histogram, so you might consider using a smaller range.  (This will make
the bucket intervals smaller).

+                          pending_request_count);
 }
 
 void HttpStreamFactoryImpl::DumpMemoryStats(
     base::trace_event::ProcessMemoryDump* pmd,
     const std::string& parent_absolute_name) const {
   if (job_controller_set_.empty())
     return;
   std::string name =
       base::StringPrintf("%s/stream_factory", parent_absolute_name.c_str());
   base::trace_event::MemoryAllocatorDump* factory_dump =
@@ skipping 29 matching lines @@
   factory_dump->AddScalar("main_job_count",
                           base::trace_event::MemoryAllocatorDump::kUnitsObjects,
                           main_job_count);
   // The number of preconnect controllers.
   factory_dump->AddScalar("preconnect_count",
                           base::trace_event::MemoryAllocatorDump::kUnitsObjects,
                           preconnect_controller_count);
 }
 
 }  // namespace net