[Extensions Bindings] Introduce a supportsLazyListeners property

extensions/browser/event_router.h

 // Copyright (c) 2012 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.
 
 #ifndef EXTENSIONS_BROWSER_EVENT_ROUTER_H_
 #define EXTENSIONS_BROWSER_EVENT_ROUTER_H_
 
 #include <set>
 #include <string>
 #include <unordered_map>
@@ skipping 216 matching lines @@
   // |did_enqueue| should be true if the event was queued waiting for a process
   // to start, like an event page.
   void ReportEvent(events::HistogramValue histogram_value,
                    const Extension* extension,
                    bool did_enqueue);
 
   LazyEventDispatchUtil* lazy_event_dispatch_util() {
     return &lazy_event_dispatch_util_;
   }
 
+  // Returns true if there is a registered lazy listener for the given
+  // |event_name|.
+  bool HasLazyEventListenerForTesting(const std::string& event_name);
+
  private:
   friend class EventRouterFilterTest;
   friend class EventRouterTest;
 
   enum class RegisteredEventType {
     kLazy,
     kServiceWorker,
   };
 
   // TODO(gdk): Document this.
@@ skipping 196 matching lines @@
   const std::string event_name;
 
   const std::string extension_id;
   const GURL listener_url;
   content::BrowserContext* const browser_context;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EVENT_ROUTER_H_