[Extensions Bindings] Introduce a supportsLazyListeners property

extensions/renderer/resources/guest_view/web_view/web_view_events.js

 // Copyright 2014 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.
 
 // Event management for WebView.
 
 var CreateEvent = require('guestViewEvents').CreateEvent;
 var DeclarativeWebRequestSchema =
     requireNative('schema_registry').GetSchema('declarativeWebRequest');
 var GuestViewEvents = require('guestViewEvents').GuestViewEvents;
@@ skipping 20 matching lines @@
     return bindingUtil.createCustomDeclarativeEvent(
         name, options.actions, options.conditions, webviewId || 0);
   }
   if (!jsEvent)
     jsEvent = require('event_bindings').Event;
   return new jsEvent(name, schema, options, webviewId);
 }
 
 function createCustomEvent(name, schema, options) {
   if (bindingUtil)
-    return bindingUtil.createCustomEvent(name, undefined, false);
+    return bindingUtil.createCustomEvent(name, undefined, false, false);
   if (!jsEvent)
     jsEvent = require('event_bindings').Event;
   return new jsEvent(name, schema, options);

[lazyboy, 2017/07/14 00:04:42]

Can we DCHECK options.supportsLazyEvents == false?

[Devlin, 2017/07/14 15:37:54]

Good idea; done.

 }
 
 function createOnMessageEvent(name, schema, options, webviewId) {
   var subEventName = name + '/' + IdGenerator.GetNextId();
   var newEvent = createCustomEvent(subEventName, schema, options);
 
   var view = GuestViewInternalNatives.GetViewFromID(webviewId || 0);
   if (view) {
     view.events.addScopedListener(
         WebRequestMessageEvent,
@@ skipping 259 matching lines @@
   }
 };
 
 WebViewEvents.prototype.handleSizeChangedEvent = function(event, eventName) {
   var webViewEvent = this.makeDomEvent(event, eventName);
   this.view.onSizeChanged(webViewEvent);
 };
 
 // Exports.
 exports.$set('WebViewEvents', WebViewEvents);