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

net/http/http_network_session.cc

Index: net/http/http_network_session.cc
diff --git a/net/http/http_network_session.cc b/net/http/http_network_session.cc
index 3908d7437f9dbfc6f78f6c84d5cb7737278d8afb..cbfee2be4c833539457eba898ad7c39f650e4bde 100644
--- a/net/http/http_network_session.cc
+++ b/net/http/http_network_session.cc
@@ -9,6 +9,7 @@
 #include "base/compiler_specific.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/values.h"
@@ -35,6 +36,10 @@ namespace {
 net::ClientSocketPoolManager* CreateSocketPoolManager(
     net::HttpNetworkSession::SocketPoolType pool_type,
     const 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 CreateSocketPoolManager"));
   // TODO(yutak): Differentiate WebSocket pool manager and allow more
   // simultaneous connections for WebSockets.
   return new net::ClientSocketPoolManagerImpl(
@@ -156,6 +161,10 @@ HttpNetworkSession::HttpNetworkSession(const Params& params)
   DCHECK(proxy_service_);
   DCHECK(ssl_config_service_.get());
   CHECK(http_server_properties_);
+  // TODO(michaeln): Remove ScopedTracker below once crbug.com/454983 is fixed
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "454983 HttpNetworkSession::HttpNetworkSession"));
 
   for (int i = ALTERNATE_PROTOCOL_MINIMUM_VALID_VERSION;
        i <= ALTERNATE_PROTOCOL_MAXIMUM_VALID_VERSION; ++i) {