Add more instrumentation to track down jank.

net/proxy/proxy_service.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/proxy/proxy_service.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 1374 matching lines @@
     }
   }
 
   net_log.EndEvent(NetLog::TYPE_PROXY_SERVICE);
   return result_code;
 }
 
 void ProxyService::SetProxyScriptFetchers(
     ProxyScriptFetcher* proxy_script_fetcher,
     DhcpProxyScriptFetcher* dhcp_proxy_script_fetcher) {
+  // TODO(eroman): Remove once crbug.com/454983 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "454983 ProxyService::SetProxyScriptFetchers"));
   DCHECK(CalledOnValidThread());
   State previous_state = ResetProxyConfig(false);
   proxy_script_fetcher_.reset(proxy_script_fetcher);
   dhcp_proxy_script_fetcher_.reset(dhcp_proxy_script_fetcher);
   if (previous_state != STATE_NONE)
     ApplyProxyConfigIfAvailable();
 }
 
 ProxyScriptFetcher* ProxyService::GetProxyScriptFetcher() const {
   DCHECK(CalledOnValidThread());
@@ skipping 204 matching lines @@
   State previous_state = ResetProxyConfig(false);
   if (previous_state != STATE_NONE)
     ApplyProxyConfigIfAvailable();
 }
 
 void ProxyService::OnDNSChanged() {
   OnIPAddressChanged();
 }
 
 }  // namespace net