Set up the infrastructure for Extension event metrics.

chrome/browser/extensions/api/signed_in_devices/signed_in_devices_manager.cc

 // Copyright 2013 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 "chrome/browser/extensions/api/signed_in_devices/signed_in_devices_manager.h"
 
 #include <string>
 #include <vector>
 
 #include "base/lazy_instance.h"
@@ skipping 60 matching lines @@
        ++it) {
     linked_ptr<api::signed_in_devices::DeviceInfo> api_device =
         make_linked_ptr(new api::signed_in_devices::DeviceInfo);
     FillDeviceInfo(*(*it), api_device.get());
     args.push_back(api_device);
   }
 
   scoped_ptr<base::ListValue> result =
       api::signed_in_devices::OnDeviceInfoChange::Create(args);
   scoped_ptr<Event> event(new Event(
-      api::signed_in_devices::OnDeviceInfoChange::kEventName,
+      events::UNKNOWN, api::signed_in_devices::OnDeviceInfoChange::kEventName,
       result.Pass()));
 
   event->restrict_to_browser_context = profile_;
 
   EventRouter::Get(profile_)->DispatchEventToExtension(
       extension_id_, event.Pass());
 }
 
 static base::LazyInstance<
     BrowserContextKeyedAPIFactory<SignedInDevicesManager> > g_factory =
@@ skipping 67 matching lines @@
 }
 
 void SignedInDevicesManager::OnExtensionUnloaded(
     content::BrowserContext* browser_context,
     const Extension* extension,
     UnloadedExtensionInfo::Reason reason) {
   RemoveChangeObserverForExtension(extension->id());
 }
 
 }  // namespace extensions