Allow extension APIs to be called from WebUI.

extensions/browser/event_router.h

Index: extensions/browser/event_router.h
diff --git a/extensions/browser/event_router.h b/extensions/browser/event_router.h
index 79a0c944d4eb06ddb3e43aebab6cb913e2d7f10f..ec408ce83b97e9e826f17bac02f989669bd2fc88 100644
--- a/extensions/browser/event_router.h
+++ b/extensions/browser/event_router.h
@@ -322,6 +322,10 @@ struct Event {
   // allowing the caller to provide different arguments depending on the
   // extension and profile. This is guaranteed to be called synchronously with
   // DispatchEvent, so callers don't need to worry about lifetime.
+  //
+  // NOTE: the Extension argument to this may be NULL if this event if it's

[Ken Rockot(use gerrit already), 2014/07/18 22:33:40]

nit: in/on/for* (not if) this event?

[not at google - send to devlin, 2014/07/18 23:28:35]

Done. I had way too many words in here.

+  // possible for this event to be dispatched to non-extension processes, like
+  // WebUI.
   WillDispatchCallback will_dispatch_callback;
 
   // If true, this event will always be dispatched to ephemeral apps, regardless