[Extensions] Add a test for removing non-lazy listeners on page tear down

Add a test that non-lazy listeners are removed when the event page is
torn down.

Bug: None

Change-Id: Icdc1d1e5e6bc6dbc05f6b99ae36da1de2ffaccb5
Reviewed-on: https://chromium-review.googlesource.com/695644
Reviewed-by: Istiaque Ahmed <[email protected]>
Commit-Queue: Devlin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#506614}
diff --git a/extensions/browser/event_router.h b/extensions/browser/event_router.h
index a7170df..6596fa85 100644
--- a/extensions/browser/event_router.h
+++ b/extensions/browser/event_router.h
@@ -236,9 +236,10 @@
     return &lazy_event_dispatch_util_;
   }
 
-  // Returns true if there is a registered lazy listener for the given
+  // Returns true if there is a registered lazy/non-lazy listener for the given
   // |event_name|.
   bool HasLazyEventListenerForTesting(const std::string& event_name);
+  bool HasNonLazyEventListenerForTesting(const std::string& event_name);
 
  private:
   friend class EventRouterFilterTest;