Fix crash in blocked input event warning.

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 77 matching lines @@
     return frameHost->settings().blockedMainThreadEventsWarningThreshold();
 }
 
 void reportBlockedEvent(ExecutionContext* context, const Event* event, RegisteredEventListener* registeredListener, double delayedSeconds)
 {
     if (registeredListener->listener()->type() != EventListener::JSEventListenerType)
         return;
 
     V8AbstractEventListener* v8Listener = V8AbstractEventListener::cast(registeredListener->listener());
     v8::HandleScope handles(v8Listener->isolate());
+    v8::Local<v8::Context> v8Context = toV8Context(context, v8Listener->world());
+    if (v8Context.IsEmpty())
+        return;
+    v8::Context::Scope contextScope(v8Context);
     v8::Local<v8::Object> handler = v8Listener->getListenerObject(context);
 
     String messageText = String::format(
         "Handling of '%s' input event was delayed for %ld ms due to main thread being busy. "
         "Consider marking event handler as 'passive' to make the page more responive.",
         event->type().getString().utf8().data(), lround(delayedSeconds * 1000));
 
     v8::Local<v8::Function> function = eventListenerEffectiveFunction(v8Listener->isolate(), handler);
     OwnPtr<SourceLocation> location = SourceLocation::fromFunction(function);
     ConsoleMessage* message = ConsoleMessage::create(JSMessageSource, WarningMessageLevel, messageText, std::move(location));
@@ skipping 530 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