Set up the infrastructure for Extension event metrics.

chrome/browser/extensions/api/terminal/terminal_private_api.cc

Index: chrome/browser/extensions/api/terminal/terminal_private_api.cc
diff --git a/chrome/browser/extensions/api/terminal/terminal_private_api.cc b/chrome/browser/extensions/api/terminal/terminal_private_api.cc
index 76eb37541f654cd036bd1ac9338b17211c4bfd33..ca77af75d320899af9f3a8f18fee930db8063e85 100644
--- a/chrome/browser/extensions/api/terminal/terminal_private_api.cc
+++ b/chrome/browser/extensions/api/terminal/terminal_private_api.cc
@@ -64,6 +64,7 @@ void NotifyProcessOutput(Profile* profile,
   extensions::EventRouter* event_router = extensions::EventRouter::Get(profile);
   if (profile && event_router) {
     scoped_ptr<extensions::Event> event(new extensions::Event(
+        extensions::events::UNKNOWN,
         terminal_private::OnProcessOutput::kEventName, args.Pass()));
         event_router->DispatchEventToExtension(extension_id, event.Pass());
   }