[Reland][Extensions Bindings] Add support for filtered events

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:
-  using Listeners = std::vector<v8::Global<v8::Function>>;
-  using ListenersChangedMethod =
-      base::Callback<void(binding::EventListenersChanged,
-                          v8::Local<v8::Context>)>;
-
-  EventEmitter(const binding::RunJSFunction& run_js,
-               const ListenersChangedMethod& listeners_changed);
+  EventEmitter(bool supports_filters,
+               std::unique_ptr<APIEventListeners> listeners,
+               const binding::RunJSFunction& run_js);
   ~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);
+            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();
+  void Invalidate(v8::Local<v8::Context> context);
 
-  const Listeners* listeners() const { return &listeners_; }
+  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;
 
-  // The event listeners associated with this event.
-  // TODO(devlin): Having these listeners held as v8::Globals means that we
-  // need to worry about cycles when a listener holds a reference to the event,
-  // e.g. EventEmitter -> Listener -> EventEmitter. Right now, we handle that by
-  // requiring Invalidate() to be called, but that means that events that aren't
-  // Invalidate()'d earlier can leak until context destruction. We could
-  // circumvent this by storing the listeners strongly in a private propery
-  // (thus traceable by v8), and optionally keep a weak cache on this object.
-  Listeners listeners_;
+  // Whether the event supports filters.
+  bool supports_filters_ = false;
+
+  std::unique_ptr<APIEventListeners> listeners_;
 
   binding::RunJSFunction run_js_;
 
-  ListenersChangedMethod listeners_changed_;
-
   DISALLOW_COPY_AND_ASSIGN(EventEmitter);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_EVENT_EMITTER_H_