Additional tracing and histogram in Extensions startup.

components/keyed_service/core/keyed_service_factory.cc

Index: components/keyed_service/core/keyed_service_factory.cc
diff --git a/components/keyed_service/core/keyed_service_factory.cc b/components/keyed_service/core/keyed_service_factory.cc
index 261ff29d556c319e143b8fe9e6646c77cf13a29d..1417bab80a39e88278147bd333e60854f13f5890 100644
--- a/components/keyed_service/core/keyed_service_factory.cc
+++ b/components/keyed_service/core/keyed_service_factory.cc
@@ -6,6 +6,7 @@
 
 #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"
 
@@ -58,6 +59,7 @@ KeyedService* KeyedServiceFactory::SetTestingFactoryAndUse(
 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;