RDH: Add some more instrumentation to figure out jank in RDH.

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 6c4da44bb62f2d767769067b9db652e13312000d..a80d6f300d149756bdacdf390b0aba374a1109ef 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -2184,6 +2184,11 @@ ResourceDispatcherHostImpl::GetLoadInfoForAllRoutes() {
               "455952 ResourceDispatcherHostImpl::GetLoadInfoForAllRoutes2"));
       upload_progress = request->GetUploadProgress();
     }
+
+    tracked_objects::ScopedTracker tracking_profile4(

[eroman, 2015/02/27 21:25:52]

I would suggest measuring TimeTicks manually for these sections, and accumulate
it over the entire pending_loaders_ before reporting it to the profiler.

The reason I suggest that is it might be more of the multiplicative effect that
leads to the jank than any individual one.

Either way, LGTM

[mmenke, 2015/02/27 21:50:22]

Good point.  For now, I think I'll just do this and look at aggregate CPU usage
(Which, admittedly, is much different from "jank").  Could end up improving the
average case but not the worst/janky case, but this method is up there when it
comes to total runtime on the IOThread, too, so I don't think that would be a
waste of time.

Admittedly, being one of the largest aggregate consumers of CPU time on the IO
thread doesn't exactly mean it consumes a huge amount of CPU time in an absolute
sense, but it really shouldn't be up there.

+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "455952 ResourceDispatcherHostImpl::GetLoadInfoForAllRoutes4"));
+
     LoadInfo load_info;
     load_info.url = request->url();
     {
@@ -2197,8 +2202,17 @@ ResourceDispatcherHostImpl::GetLoadInfoForAllRoutes() {
     load_info.upload_size = upload_progress.size();
     load_info.upload_position = upload_progress.position();
 
+    tracked_objects::ScopedTracker tracking_profile5(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "455952 ResourceDispatcherHostImpl::GetLoadInfoForAllRoutes5"));
+
     GlobalRoutingID id(loader.second->GetRequestInfo()->GetGlobalRoutingID());
     LoadInfoMap::iterator existing = info_map->find(id);
+
+    tracked_objects::ScopedTracker tracking_profile6(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "455952 ResourceDispatcherHostImpl::GetLoadInfoForAllRoutes6"));
+
     if (existing == info_map->end() ||
         LoadInfoIsMoreInteresting(load_info, existing->second)) {
       (*info_map)[id] = load_info;