Support "once" event listener option

third_party/WebKit/Source/core/events/EventTarget.cpp

Index: third_party/WebKit/Source/core/events/EventTarget.cpp
diff --git a/third_party/WebKit/Source/core/events/EventTarget.cpp b/third_party/WebKit/Source/core/events/EventTarget.cpp
index 19d5091f15ebdd4558136670d22ba78525c43cb5..2e789148724b812c5069fe593a494e2bfd2655a0 100644
--- a/third_party/WebKit/Source/core/events/EventTarget.cpp
+++ b/third_party/WebKit/Source/core/events/EventTarget.cpp
@@ -615,6 +615,8 @@ bool EventTarget::fireEventListeners(Event* event, EventTargetData* d, EventList
             continue;
         if (event->eventPhase() == Event::kBubblingPhase && registeredListener.capture())
             continue;
+        if (registeredListener.onceBeingRemoved())

[dtapuska, 2016/08/12 18:44:02]

Is it possible to change the RegisteredListener not to be a reference but a copy
on the stack in this method and call removeEventListener before you dispatch the
event to the listener. That should prevent the re-entrancy problem the
onceBeingRemoved is trying to fix. I just wonder if it is over complicated and
could be fixed in an alternate fashion.

[Anton Obzhirov, 2016/08/15 22:18:01]

Hm, I will need to add new method to EventListenerVector to swap content of the
RegisteredEventListener instance in the vector with the new instance on stack
and then remove empty registered listener from EventListenerVector. Should be
possible to do, let me try.

+            continue;
 
         // If stopImmediatePropagation has been called, we just break out immediately, without
         // handling any more events on this target.
@@ -624,6 +626,11 @@ bool EventTarget::fireEventListeners(Event* event, EventTargetData* d, EventList
         event->setHandlingPassive(registeredListener.passive());
         bool passiveForced = registeredListener.passiveForcedForDocumentTarget();
 
+        // Mark listener for removal before executing the listener, in case the listener tries to
+        // dispatch an event that would cause it to get executed again.
+        if (registeredListener.once())
+            registeredListener.setOnceBeingRemoved();
+
         InspectorInstrumentation::NativeBreakpoint nativeBreakpoint(context, this, event);
 
         EventListener* listener = registeredListener.listener();
@@ -650,7 +657,8 @@ bool EventTarget::fireEventListeners(Event* event, EventTargetData* d, EventList
         }
 
         event->setHandlingPassive(false);
-
+        if (registeredListener.once())
+            removeEventListener(event->type(), listener, registeredListener.capture());
         RELEASE_ASSERT(i <= size);
     }
     d->firingEventIterators->removeLast();