[Extensions Bindings] Return result from event dispatch

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"
 #include "gin/wrappable.h"
 #include "v8/include/v8.h"
 
 namespace gin {
 class Arguments;
 }
 
 namespace extensions {
 class APIEventListeners;
 class EventFilteringInfo;
 
 // A gin::Wrappable Event object. One is expected to be created per event, per
 // context. Note: this object *does not* clear any events, so it must be
 // destroyed with the context to avoid leaking.
 class EventEmitter final : public gin::Wrappable<EventEmitter> {
  public:
   EventEmitter(bool supports_filters,
                std::unique_ptr<APIEventListeners> listeners,
-               const binding::RunJSFunction& run_js);
+               const binding::RunJSFunction& run_js,
+               const binding::RunJSFunctionSync& run_js_sync);
   ~EventEmitter() override;
 
   static gin::WrapperInfo kWrapperInfo;
 
   // gin::Wrappable:
   gin::ObjectTemplateBuilder GetObjectTemplateBuilder(
       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);
 
   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);
 
+  // Notifies the listeners of an event with the given |args|. If |run_sync| is
+  // true, runs JS synchronously and populates |out_values| with the results of
+  // the listeners.
+  void DispatchImpl(v8::Local<v8::Context> context,
+                    std::vector<v8::Local<v8::Value>>* args,
+                    const EventFilteringInfo* filter,
+                    bool run_sync,
+                    std::vector<v8::Global<v8::Value>>* out_values);
+
   // 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_;
+  binding::RunJSFunctionSync run_js_sync_;
 
   DISALLOW_COPY_AND_ASSIGN(EventEmitter);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_EVENT_EMITTER_H_