Remove EventSender in HTMLDetailsElement

third_party/WebKit/Source/core/html/HTMLDetailsElement.cpp

 /*
  * Copyright (C) 2010, 2011 Nokia Corporation and/or its subsidiary(-ies)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #include "core/html/HTMLDetailsElement.h"
 
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
 #include "core/CSSPropertyNames.h"
 #include "core/CSSValueKeywords.h"
 #include "core/HTMLNames.h"
 #include "core/dom/ElementTraversal.h"
+#include "core/dom/TaskRunnerHelper.h"
 #include "core/dom/Text.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/events/Event.h"
-#include "core/events/EventSender.h"
 #include "core/frame/UseCounter.h"
 #include "core/html/HTMLContentElement.h"
 #include "core/html/HTMLDivElement.h"
 #include "core/html/HTMLSummaryElement.h"
 #include "core/html/shadow/DetailsMarkerControl.h"
 #include "core/html/shadow/ShadowElementNames.h"
 #include "core/layout/LayoutBlockFlow.h"
 #include "platform/text/PlatformLocale.h"
 
 namespace blink {
@@ skipping 18 matching lines @@
     }
     return true;
   }
 
   DEFINE_INLINE_VIRTUAL_TRACE() { HTMLContentSelectFilter::trace(visitor); }
 
  private:
   FirstSummarySelectFilter() {}
 };
 
-static DetailsEventSender& detailsToggleEventSender() {
-  DEFINE_STATIC_LOCAL(DetailsEventSender, sharedToggleEventSender,
-                      (DetailsEventSender::create(EventTypeNames::toggle)));
-  return sharedToggleEventSender;
-}
-
 HTMLDetailsElement* HTMLDetailsElement::create(Document& document) {
   HTMLDetailsElement* details = new HTMLDetailsElement(document);
   details->ensureUserAgentShadowRoot();
   return details;
 }
 
 HTMLDetailsElement::HTMLDetailsElement(Document& document)
     : HTMLElement(detailsTag, document), m_isOpen(false) {
   UseCounter::count(document, UseCounter::DetailsElement);
 }
 
 HTMLDetailsElement::~HTMLDetailsElement() {}
 
-void HTMLDetailsElement::dispatchPendingEvent(DetailsEventSender* eventSender) {
-  DCHECK_EQ(eventSender, &detailsToggleEventSender());
+void HTMLDetailsElement::dispatchPendingEvent() {
   dispatchEvent(Event::create(EventTypeNames::toggle));
 }
 
 LayoutObject* HTMLDetailsElement::createLayoutObject(const ComputedStyle&) {
   return new LayoutBlockFlow(this);
 }
 
 void HTMLDetailsElement::didAddUserAgentShadowRoot(ShadowRoot& root) {
   HTMLSummaryElement* defaultSummary = HTMLSummaryElement::create(document());
   defaultSummary->appendChild(Text::create(
@@ skipping 27 matching lines @@
 void HTMLDetailsElement::parseAttribute(const QualifiedName& name,
                                         const AtomicString& oldValue,
                                         const AtomicString& value) {
   if (name == openAttr) {
     bool oldValue = m_isOpen;
     m_isOpen = !value.isNull();
     if (m_isOpen == oldValue)
       return;
 
     // Dispatch toggle event asynchronously.
-    detailsToggleEventSender().cancelEvent(this);
-    detailsToggleEventSender().dispatchEventSoon(this);
+    m_pendingEvent =

[hiroshige, 2016/11/07 09:24:55]

Here previous event is canceled (because |m_pendingEvent| is overwritten).

[haraken, 2016/11/07 09:51:01]

Hmm, we need to keep holding m_pendingEvent in order not to cancel the task...
which seems error-prone to me; i.e., if developers forget to hold the task
handle, the task will be unintentionally cancelled.

Would you help me understand why we wanted to adopt the cancel-on-destruction
semantics for TaskHandles?

+        TaskRunnerHelper::get(TaskType::DOMManipulation, &document())
+            ->postCancellableTask(
+                BLINK_FROM_HERE,
+                WTF::bind(&HTMLDetailsElement::dispatchPendingEvent,
+                          wrapPersistent(this)));
 
     Element* content = ensureUserAgentShadowRoot().getElementById(
         ShadowElementNames::detailsContent());
     DCHECK(content);
     if (m_isOpen)
       content->removeInlineStyleProperty(CSSPropertyDisplay);
     else
       content->setInlineStyleProperty(CSSPropertyDisplay, CSSValueNone);
 
     // Invalidate the LayoutDetailsMarker in order to turn the arrow signifying
@@ skipping 12 matching lines @@
 
 void HTMLDetailsElement::toggleOpen() {
   setAttribute(openAttr, m_isOpen ? nullAtom : emptyAtom);
 }
 
 bool HTMLDetailsElement::isInteractiveContent() const {
   return true;
 }
 
 }  // namespace blink