Add UMA that periodically logs number of outstanding requests

content/browser/loader/resource_dispatcher_host_impl.h

Index: content/browser/loader/resource_dispatcher_host_impl.h
diff --git a/content/browser/loader/resource_dispatcher_host_impl.h b/content/browser/loader/resource_dispatcher_host_impl.h
index 3f5aa959c691d7b6d091ec99a4a24a06c1ffc08a..70f377e30619a43c1c6872efd39212591199572b 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.h
+++ b/content/browser/loader/resource_dispatcher_host_impl.h
@@ -457,6 +457,13 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
       int count,
       ResourceRequestInfoImpl* info);
 
+  // Called from IncrementOutstandingRequestsCount to update the per-tab
+  // request stats in |outstanding_requests_per_tab_map_|.
+  // TODO(ksakamoto): This is just for temporary metrics collection for the
+  // Loading Dispatcher v0 (crbug.com/723233), and will be removed soon.
+  void IncrementOutstandingRequestsPerTab(int count,
+                                          const ResourceRequestInfoImpl& info);
+
   // Estimate how much heap space |request| will consume to run.
   static int CalculateApproximateMemoryCost(net::URLRequest* request);
 
@@ -513,6 +520,10 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
   // Checks all pending requests and updates the load info if necessary.
   void UpdateLoadInfo();
 
+  // Records statistics about outstanding requests since the last call, and
+  // reset the stats.
+  void RecordOutstandingRequestsStats();
+
   // Resumes or cancels (if |cancel_requests| is true) any blocked requests.
   void ProcessBlockedRequestsForRoute(
       const GlobalFrameRoutingId& global_routing_id,
@@ -695,6 +706,10 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
       bool must_download,
       bool is_new_request);
 
+  // Returns true if there are two or more tabs that are not network 2-quiet
+  // (i.e. have at least three outstanding requests).
+  bool HasRequestsFromMultipleActiveTabs();
+
   LoaderMap pending_loaders_;
 
   // Collection of temp files downloaded for child processes via
@@ -710,6 +725,10 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
   // not empty and at least one RenderViewHost is loading.
   std::unique_ptr<base::RepeatingTimer> update_load_states_timer_;
 
+  // A timer that periodically calls RecordOutstandingRequestsStats.
+  std::unique_ptr<base::RepeatingTimer>
+      record_outstanding_requests_stats_timer_;
+
   // Request ID for browser initiated requests. request_ids generated by
   // child processes are counted up from 0, while browser created requests
   // start at -2 and go down from there. (We need to start at -2 because -1 is
@@ -732,6 +751,14 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
   typedef std::map<int, OustandingRequestsStats> OutstandingRequestsStatsMap;
   OutstandingRequestsStatsMap outstanding_requests_stats_map_;
 
+  // Maps (child_id, route_id) to the number of outstanding requests.
+  // Used only when OOPIF is not enabled, since in OOPIF modes routing_id
+  // doesn't represent tabs.
+  // TODO(ksakamoto): This is just for temporary metrics collection for the
+  // Loading Dispatcher v0 (crbug.com/723233), and will be removed soon.
+  typedef std::map<std::pair<int, int>, int> OutstandingRequestsPerTabMap;
+  OutstandingRequestsPerTabMap outstanding_requests_per_tab_map_;
+
   // |num_in_flight_requests_| is the total number of requests currently issued
   // summed across all renderers.
   int num_in_flight_requests_;
@@ -763,6 +790,15 @@ class CONTENT_EXPORT ResourceDispatcherHostImpl
   // Largest number of outstanding requests seen so far in any single process.
   int largest_outstanding_request_per_process_count_seen_;
 
+  // Largest number of outstanding requests seen since the last call to
+  // RecordOutstandingRequestsStats.
+  int peak_outstanding_request_count_ = 0;
+
+  // Largest number of outstanding requests seen while there are outstanding
+  // requests from two or more tabs, since the last call to
+  // RecordOutstandingRequestsStats.
+  int peak_outstanding_request_count_multitab_ = 0;
+
   // Time of the last user gesture. Stored so that we can add a load
   // flag to requests occurring soon after a gesture to indicate they
   // may be because of explicit user action.