Additional tracing and histogram in Extensions startup.

components/keyed_service/core/keyed_service_factory.cc

 // Copyright 2014 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 "components/keyed_service/core/keyed_service_factory.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
+#include "base/trace_event/trace_event.h"
 #include "components/keyed_service/core/dependency_manager.h"
 #include "components/keyed_service/core/keyed_service.h"
 
 KeyedServiceFactory::KeyedServiceFactory(const char* name,
                                          DependencyManager* manager)
     : KeyedServiceBaseFactory(name, manager) {
 }
 
 KeyedServiceFactory::~KeyedServiceFactory() {
   DCHECK(mapping_.empty());
@@ skipping 32 matching lines @@
     base::SupportsUserData* context,
     TestingFactoryFunction testing_factory) {
   DCHECK(testing_factory);
   SetTestingFactory(context, testing_factory);
   return GetServiceForContext(context, true);
 }
 
 KeyedService* KeyedServiceFactory::GetServiceForContext(
     base::SupportsUserData* context,
     bool create) {
+  TRACE_EVENT0("browser,startup", "KeyedServiceFactory::GetServiceForContext");

[Elliot Glaysher, 2015/03/04 19:06:00]

I expect that this event will be extremely spammy. All access to all components
come through this method.

   context = GetContextToUse(context);
   if (!context)
     return nullptr;
 
   // NOTE: If you modify any of the logic below, make sure to update the
   // refcounted version in refcounted_context_keyed_service_factory.cc!
   const auto& it = mapping_.find(context);
   if (it != mapping_.end())
     return it->second;
 
@@ skipping 57 matching lines @@
   SetTestingFactory(context, nullptr);
 }
 
 bool KeyedServiceFactory::HasTestingFactory(base::SupportsUserData* context) {
   return testing_factories_.find(context) != testing_factories_.end();
 }
 
 void KeyedServiceFactory::CreateServiceNow(base::SupportsUserData* context) {
   GetServiceForContext(context, true);
 }