Set up the infrastructure for Extension event metrics.

chrome/browser/extensions/api/gcd_private/gcd_private_api.cc

Index: chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
diff --git a/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc b/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
index 013ebc0b60d19597fb30bb15a9d2a4c2bffdfef6..5002c76b4c73a9ca7f9d6d34df1c7e8a3f3c13da 100644
--- a/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
+++ b/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
@@ -57,15 +57,17 @@ scoped_ptr<Event> MakeDeviceStateChangedEvent(
   scoped_ptr<base::ListValue> params =
       gcd_private::OnDeviceStateChanged::Create(device);
   scoped_ptr<Event> event(
-      new Event(gcd_private::OnDeviceStateChanged::kEventName, params.Pass()));
+      new Event(events::UNKNOWN, gcd_private::OnDeviceStateChanged::kEventName,
+                params.Pass()));
   return event.Pass();
 }
 
 scoped_ptr<Event> MakeDeviceRemovedEvent(const std::string& device) {
   scoped_ptr<base::ListValue> params =
       gcd_private::OnDeviceRemoved::Create(device);
-  scoped_ptr<Event> event(
-      new Event(gcd_private::OnDeviceRemoved::kEventName, params.Pass()));
+  scoped_ptr<Event> event(new Event(events::UNKNOWN,
+                                    gcd_private::OnDeviceRemoved::kEventName,
+                                    params.Pass()));
   return event.Pass();
 }