ScopedTrackers to help pin down where IOThread::InitSystemRequestContextOnIOThread is janky

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 9ef53eeac4556f6865d2b244199b8d94a453161e..63d13001baa24f96a97114971ac4ec4b184574f0 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -17,6 +17,7 @@
 #include "base/metrics/user_metrics.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
@@ -253,6 +254,10 @@ ConstructProxyScriptFetcherContext(IOThread::Globals* globals,
 net::URLRequestContext*
 ConstructSystemRequestContext(IOThread::Globals* globals,
                               net::NetLog* net_log) {
+  // TODO(michaeln): Remove ScopedTracker below once crbug.com/454983 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "454983 ConstructSystemRequestContext"));
   net::URLRequestContext* context = new SystemURLRequestContext;
   context->set_net_log(net_log);
   context->set_host_resolver(globals->host_resolver.get());
@@ -982,6 +987,10 @@ void IOThread::ClearHostCache() {
 
 void IOThread::InitializeNetworkSessionParams(
     net::HttpNetworkSession::Params* params) {
+  // TODO(michaeln): Remove ScopedTracker below once crbug.com/454983 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "454983 IOThread::InitializeNetworkSessionParams"));
   InitializeNetworkSessionParamsFromGlobals(*globals_, params);
 }
 
@@ -1111,9 +1120,16 @@ void IOThread::InitSystemRequestContextOnIOThread() {
   system_params.net_log = net_log_;
   system_params.proxy_service = globals_->system_proxy_service.get();
 
-  globals_->system_http_transaction_factory.reset(
-      new net::HttpNetworkLayer(
-          new net::HttpNetworkSession(system_params)));
+  {
+    // TODO(michaeln): Remove after crbug.com/454983 is fixed.
+    tracked_objects::ScopedTracker tracking_profile(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "454983 IOThread::InitSystemRequestContextOnIOThread"
+            ".HttpNetworkSession"));

[Peter Kasting, 2015/02/09 23:35:44]

Nit: Name seems slightly misleading since this is actually measuring the
HttpNetworkLayer/HttpTransactionFactory constructor costs, right?  (Since you've
instrumented HttpNetworkSession's constructor separately.)

+    globals_->system_http_transaction_factory.reset(
+        new net::HttpNetworkLayer(
+            new net::HttpNetworkSession(system_params)));
+  }
   globals_->system_url_request_job_factory.reset(
       new net::URLRequestJobFactoryImpl());
   globals_->system_request_context.reset(