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 b6196b5a5759518ddaad490125bcb550e619f540..b0952d7340ee7f20224a75e22fc08a569147fbc5 100644
--- a/third_party/WebKit/Source/core/events/EventTarget.cpp
+++ b/third_party/WebKit/Source/core/events/EventTarget.cpp
@@ -608,7 +608,7 @@ bool EventTarget::fireEventListeners(Event* event, EventTargetData* d, EventList
     bool firedListener = false;
 
     while (i < size) {
-        RegisteredEventListener& registeredListener = entry[i];
+        RegisteredEventListener registeredListener = entry[i];
 
         // Move the iterator past this event listener. This must match
         // the handling of the FiringEventIterator::iterator in
@@ -620,6 +620,12 @@ bool EventTarget::fireEventListeners(Event* event, EventTargetData* d, EventList
         if (event->eventPhase() == Event::kBubblingPhase && registeredListener.capture())
             continue;
 
+        EventListener* listener = registeredListener.listener();
+        // The listener will retained by Member<EventListener> in the registeredListener
+        // in case the listener is removed from the listener vector below.
+        if (registeredListener.once())
+            removeEventListener(event->type(), listener, registeredListener.capture());

[tkent, 2016/08/19 02:21:15]

Is it safe to remove a listener while iterating over |entry|?

[Anton Obzhirov, 2016/08/19 10:41:39]

No, it is not, thanks for pointing out. I need to update as minimum
i and size. Basically I need to do similar to what removeEventListenerInternal
does with the firing iterators.

+
         // If stopImmediatePropagation has been called, we just break out immediately, without
         // handling any more events on this target.
         if (event->immediatePropagationStopped())
@@ -630,8 +636,6 @@ bool EventTarget::fireEventListeners(Event* event, EventTargetData* d, EventList
 
         InspectorInstrumentation::NativeBreakpoint nativeBreakpoint(context, this, event);
 
-        EventListener* listener = registeredListener.listener();
-
         // To match Mozilla, the AT_TARGET phase fires both capturing and bubbling
         // event listeners, even though that violates some versions of the DOM spec.
         listener->handleEvent(context, event);