[Extensions Bindings] Request JS execution from messaging bindings

extensions/renderer/event_emitter.h

 // Copyright 2016 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_RENDERER_EVENT_EMITTER_H_
 #define EXTENSIONS_RENDERER_EVENT_EMITTER_H_
 
 #include <vector>
 
 #include "extensions/renderer/api_binding_types.h"
@@ skipping 25 matching lines @@
       v8::Isolate* isolate) final;
 
   void Fire(v8::Local<v8::Context> context,
             std::vector<v8::Local<v8::Value>>* args,
             const EventFilteringInfo* filter);
 
   // Removes all listeners and marks this object as invalid so that no more
   // are added.
   void Invalidate(v8::Local<v8::Context> context);
 
+  // TODO(devlin): Consider making this a test-only method and exposing
+  // HasListeners() instead.
   size_t GetNumListeners() const;
 
  private:
   // Bound methods for the Event JS object.
   void AddListener(gin::Arguments* arguments);
   void RemoveListener(gin::Arguments* arguments);
   bool HasListener(v8::Local<v8::Function> function);
   bool HasListeners();
   void Dispatch(gin::Arguments* arguments);
 
   // Whether or not this object is still valid; false upon context release.
   // When invalid, no listeners can be added or removed.
   bool valid_ = true;
 
   // Whether the event supports filters.
   bool supports_filters_ = false;
 
   std::unique_ptr<APIEventListeners> listeners_;
 
   binding::RunJSFunction run_js_;
 
   DISALLOW_COPY_AND_ASSIGN(EventEmitter);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_EVENT_EMITTER_H_