Add UMA for number of outstanding requests in ResourceDispatcherHostImpl

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index a9c9157800379d6417aed7d77b1a522fe829b111..cdaadd1d734d2412e648046a1552d15df34354c2 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -137,7 +137,7 @@ static ResourceDispatcherHostImpl* g_resource_dispatcher_host;
 const int kUpdateLoadStatesIntervalMsec = 250;
 
 // Maximum byte "cost" of all the outstanding requests for a renderer.
-// See delcaration of |max_outstanding_requests_cost_per_process_| for details.
+// See declaration of |max_outstanding_requests_cost_per_process_| for details.
 // This bound is 25MB, which allows for around 6000 outstanding requests.
 const int kMaxOutstandingRequestsCostPerProcess = 26214400;
 
@@ -350,6 +350,8 @@ ResourceDispatcherHostImpl::ResourceDispatcherHostImpl(
           max_num_in_flight_requests_ * kMaxRequestsPerProcessRatio)),
       max_outstanding_requests_cost_per_process_(
           kMaxOutstandingRequestsCostPerProcess),
+      largest_outstanding_request_count_seen_(0),
+      largest_outstanding_request_per_process_count_seen_(0),
       delegate_(nullptr),
       loader_delegate_(nullptr),
       allow_cross_origin_auth_prompt_(false),
@@ -1904,6 +1906,20 @@ ResourceDispatcherHostImpl::IncrementOutstandingRequestsCount(
   DCHECK_GE(stats.num_requests, 0);
   UpdateOutstandingRequestsStats(*info, stats);
 
+  if (num_in_flight_requests_ > largest_outstanding_request_count_seen_) {

[Charlie Harrison, 2017/04/19 23:08:28]

I wonder if this would be better logged in Shutdown? Then you only get the max
requests for a given session.

[xunjieli, 2017/04/20 13:34:11]

Similar to crbug.com/704988, Chrome on Android never shuts down and some users 
seldom shut down their browser. 

[Charlie Harrison, 2017/04/20 13:39:16]

OK, this LGTM but it would be preferable to hook into NetworkMetricsProvider if
it's feasible.

[xunjieli, 2017/04/20 20:06:08]

Acknowledged. I didn't find a way to hook it up with NetworkMetricsProvider. I
don't think content/ can depend on components/, can it?

[Charlie Harrison, 2017/04/20 20:09:14]

One possible way to implement it would be to pull information out of the RDH
singleton in the component. It's pretty ugly though. We'd have to change it for
the network service later too. Let's just land this, and loop back if we think
the data is not up to snuff.

[xunjieli, 2017/04/20 20:14:15]

Acknowledged. Thanks.

+    largest_outstanding_request_count_seen_ = num_in_flight_requests_;
+    UMA_HISTOGRAM_COUNTS_1M(
+        "Net.ResourceDispatcherHost.OutstandingRequests.Total",
+        largest_outstanding_request_count_seen_);
+  }
+
+  if (stats.num_requests > largest_outstanding_request_count_seen_) {
+    largest_outstanding_request_per_process_count_seen_ = stats.num_requests;
+    UMA_HISTOGRAM_COUNTS_1M(
+        "Net.ResourceDispatcherHost.OutstandingRequests.PerProcess",
+        largest_outstanding_request_per_process_count_seen_);
+  }
+
   return stats;
 }