Add histograms to track the number of job controller and job that are

net/http/http_stream_factory_impl.cc

Index: net/http/http_stream_factory_impl.cc
diff --git a/net/http/http_stream_factory_impl.cc b/net/http/http_stream_factory_impl.cc
index 0a742d1284204e4fcedf919df133dab72df2417f..06d223ad11e7aaa27a5d49c434c7995dc5c45143 100644
--- a/net/http/http_stream_factory_impl.cc
+++ b/net/http/http_stream_factory_impl.cc
@@ -104,6 +104,28 @@ HttpStreamFactoryImpl::HttpStreamFactoryImpl(HttpNetworkSession* session,
 HttpStreamFactoryImpl::~HttpStreamFactoryImpl() {
   DCHECK(request_map_.empty());
   DCHECK(spdy_session_request_map_.empty());
+  size_t alt_job_count = 0;
+  size_t main_job_count = 0;
+  size_t preconnect_controller_count = 0;
+  for (const auto& it : job_controller_set_) {
+    // For a preconnect controller, it should have exactly the main job.
+    if (it->is_preconnect()) {
+      preconnect_controller_count++;
+      continue;
+    }
+    // For non-preconnects.

[xunjieli, 2017/03/17 00:47:56]

Suggest add a DCHECK(it->HasPendingAltJob()||it->HasPendingMainJob()) here to
make sure we won't have JobController hanging around when there aren't any jobs.

[Zhongyi Shi, 2017/03/17 02:02:29]

Done.

+    if (it->HasPendingAltJob())
+      alt_job_count++;
+    if (it->HasPendingMainJob())
+      main_job_count++;
+  }
+  UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfJobController",

[xunjieli, 2017/03/17 00:47:56]

This histogram is not necessary, right?
We can deduce this from the other three. In other words, this histogram should
strictly follow the trend of the other three.

[Zhongyi Shi, 2017/03/17 02:02:29]

Well, that's not exactly true. There might be JobController having both alt job
and main job uncleaned up theoretically. Although we shouldn't run into that
case since all the requests should be handed out to clients.
https://cs.chromium.org/chromium/src/net/http/http_stream_factory_impl.h?l=169

[xunjieli, 2017/03/17 13:05:23]

Right, that's why I suggested using a DCHECK(it->HasPendingAltJob() ||
it->HasPendingMainJob()) so we should catch that unlikely case.

+                          job_controller_set_.size());
+  UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfPreconnect",
+                          preconnect_controller_count);
+  UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfAltJob", alt_job_count);

[xunjieli, 2017/03/17 00:47:56]

For someone who might not know this code, I suggest make a distinction in the
name of the histograms regarding preconnect and nonpreconnect.


"CountOfAltJob" -> "CountOfNonPreconnectAltJob"
"CountOfMainJob" -> "CountOfNonPreconnectMainJob"

[Zhongyi Shi, 2017/03/17 02:02:29]

Done.

+  UMA_HISTOGRAM_COUNTS_1M("Net.JobControllerSet.CountOfMainJob",
+                          main_job_count);
 }
 
 HttpStreamRequest* HttpStreamFactoryImpl::RequestStream(