Remove EventSender in HTMLDetailsElement

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

Index: third_party/WebKit/Source/core/html/HTMLDetailsElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLDetailsElement.cpp b/third_party/WebKit/Source/core/html/HTMLDetailsElement.cpp
index 52d2b418ab87a0a36e8c1a07e201a81dba309e50..5a34cbf08bc6c35a3bda87f430fd84fe50aa0e87 100644
--- a/third_party/WebKit/Source/core/html/HTMLDetailsElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLDetailsElement.cpp
@@ -25,10 +25,10 @@
 #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"
@@ -67,12 +67,6 @@ class FirstSummarySelectFilter final : public HTMLContentSelectFilter {
   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();
@@ -86,8 +80,7 @@ HTMLDetailsElement::HTMLDetailsElement(Document& document)
 
 HTMLDetailsElement::~HTMLDetailsElement() {}
 
-void HTMLDetailsElement::dispatchPendingEvent(DetailsEventSender* eventSender) {
-  DCHECK_EQ(eventSender, &detailsToggleEventSender());
+void HTMLDetailsElement::dispatchPendingEvent() {
   dispatchEvent(Event::create(EventTypeNames::toggle));
 }
 
@@ -135,8 +128,12 @@ void HTMLDetailsElement::parseAttribute(const QualifiedName& name,
       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());