[Extensions Bindings] Introduce a supportsLazyListeners property

extensions/renderer/bindings/api_event_handler.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_BINDINGS_API_EVENT_HANDLER_H_
 #define EXTENSIONS_RENDERER_BINDINGS_API_EVENT_HANDLER_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 10 matching lines @@
 namespace extensions {
 class ExceptionHandler;
 struct EventFilteringInfo;
 
 // The object to handle API events. This includes vending v8::Objects for the
 // event; handling adding, removing, and querying listeners; and firing events
 // to subscribed listeners. Designed to be used across JS contexts, but on a
 // single thread.
 class APIEventHandler {
  public:
-  // The callback to be called when event listeners change. |was_manual|
-  // indicates that the change was due to an extension calling addListener or
-  // removeListener, rather than through something like context destruction.
+  // The callback to be called when event listeners change.
+  // |update_lazy_listeners| indicates that the change was due to an extension
+  // calling addListener or removeListener on an event that supports lazy
+  // listeners, rather than through something like context destruction or
+  // removing a listener from an event that doesn't support lazy listeners.
   // See also APIEventListeners.
   using EventListenersChangedMethod =
       base::Callback<void(const std::string& event_name,
                           binding::EventListenersChanged,
                           const base::DictionaryValue* filter,
-                          bool was_manual,
+                          bool update_lazy_listeners,
                           v8::Local<v8::Context>)>;
 
   APIEventHandler(const binding::RunJSFunction& call_js,
                   const binding::RunJSFunctionSync& call_js_sync,
                   const EventListenersChangedMethod& listeners_changed,
                   ExceptionHandler* exception_handler);
   ~APIEventHandler();
 
   // Returns a new v8::Object for an event with the given |event_name|. If
   // |notify_on_change| is true, notifies whenever listeners state is changed.
+  // TODO(devlin): Maybe worth creating a Params struct to hold the event
+  // information?
   v8::Local<v8::Object> CreateEventInstance(const std::string& event_name,
                                             bool supports_filters,
+                                            bool supports_lazy_listeners,
                                             int max_listeners,
                                             bool notify_on_change,
                                             v8::Local<v8::Context> context);
 
   // Creates a new event without any name. This is used by custom bindings when
   // the entirety of the logic for the event is contained in the renderer. These
   // events do not notify of new/removed listeners or allow for dispatching
   // through FireEventInContext().
   v8::Local<v8::Object> CreateAnonymousEventInstance(
       v8::Local<v8::Context> context);
@@ skipping 47 matching lines @@
   // The exception handler associated with the bindings system; guaranteed to
   // outlive this object.
   ExceptionHandler* const exception_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(APIEventHandler);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_BINDINGS_API_EVENT_HANDLER_H_