Emit a console warning when blocking event listener is delayed for too long

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  *           (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ skipping 398 matching lines @@
         if (LocalDOMWindow* executingWindow = this->executingWindow())
             UseCounter::count(executingWindow->document(), UseCounter::DOMFocusInOutEvent);
     } else if (event->type() == EventTypeNames::focusin || event->type() == EventTypeNames::focusout) {
         if (LocalDOMWindow* executingWindow = this->executingWindow())
             UseCounter::count(executingWindow->document(), UseCounter::FocusInOutEvent);
     } else if (event->type() == EventTypeNames::textInput) {
         if (LocalDOMWindow* executingWindow = this->executingWindow())
             UseCounter::count(executingWindow->document(), UseCounter::TextInputFired);
     }
 
+    ExecutionContext* context = getExecutionContext();
+    if (!context)
+        return;
+
     size_t i = 0;
     size_t size = entry.size();
     if (!d->firingEventIterators)
         d->firingEventIterators = adoptPtr(new FiringEventIteratorVector);
     d->firingEventIterators->append(FiringEventIterator(event->type(), i, size));
+
+    bool shouldReportBlockedEvent = InspectorInstrumentation::shouldReportBlockedEvent(context, event);

[pfeldman, 2016/05/04 22:58:01]

Lets instead call EventTarget::logBlockedEventsToConsole();

+    double eventBlockedTime = shouldReportBlockedEvent ? WTF::monotonicallyIncreasingTime() - event->platformTimeStamp() : 0;
+
     while (i < size) {
         RegisteredEventListener& registeredListener = entry[i];
 
         // Move the iterator past this event listener. This must match
         // the handling of the FiringEventIterator::iterator in
         // EventTarget::removeEventListener.
         ++i;
 
         if (event->eventPhase() == Event::CAPTURING_PHASE && !registeredListener.useCapture)
             continue;
         if (event->eventPhase() == Event::BUBBLING_PHASE && registeredListener.useCapture)
             continue;
 
         // If stopImmediatePropagation has been called, we just break out immediately, without
         // handling any more events on this target.
         if (event->immediatePropagationStopped())
             break;
 
-        ExecutionContext* context = getExecutionContext();
-        if (!context)
-            break;
-
         event->setHandlingPassive(registeredListener.passive);
 
         InspectorInstrumentation::NativeBreakpoint nativeBreakpoint(context, this, event);
 
         // To match Mozilla, the AT_TARGET phase fires both capturing and bubbling
         // event listeners, even though that violates some versions of the DOM spec.
         registeredListener.listener->handleEvent(context, event);
+
+        if (shouldReportBlockedEvent && !registeredListener.passive && !registeredListener.blockedEventWarningEmitted && !event->defaultPrevented())
+            InspectorInstrumentation::reportBlockedEvent(context, event, &registeredListener, eventBlockedTime);
+
         event->setHandlingPassive(false);
 
         RELEASE_ASSERT(i <= size);
     }
     d->firingEventIterators->removeLast();
 }
 
 DispatchEventResult EventTarget::dispatchEventResult(const Event& event)
 {
     if (event.defaultPrevented())
@@ skipping 28 matching lines @@
     // they have one less listener to invoke.
     if (d->firingEventIterators) {
         for (size_t i = 0; i < d->firingEventIterators->size(); ++i) {
             d->firingEventIterators->at(i).iterator = 0;
             d->firingEventIterators->at(i).end = 0;
         }
     }
 }
 
 } // namespace blink