Use method registration approach for creating events on core and modules.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index d8bae3c9c0648b2e235041b3f80cf4539a4df28d..0056af95da6e475c6a57c8f9563f1f9aadebbda7 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -3922,12 +3922,26 @@ void Document::enqueueResizeEvent()
     ensureScriptedAnimationController().enqueuePerFrameEvent(event.release());
 }
 
-PassRefPtrWillBeRawPtr<Event> Document::createEvent(const String& eventType, ExceptionState& exceptionState)
+Document::EventFactorySet& Document::eventFactories()
+{
+    DEFINE_STATIC_LOCAL(EventFactorySet, s_eventFactory, ());
+    return s_eventFactory;
+}
+
+void Document::registerEventFactory(EventFactoryBase* eventFactory)
 {
-    RefPtrWillBeRawPtr<Event> event = EventFactory::create(eventType);
-    if (event)
-        return event.release();
+    ASSERT(!eventFactories().contains(eventFactory));
+    eventFactories().add(eventFactory);
+}
 
+PassRefPtrWillBeRawPtr<Event> Document::createEvent(const String& eventType, ExceptionState& exceptionState)
+{
+    RefPtrWillBeRawPtr<Event> event = nullptr;
+    for (EventFactorySet::const_iterator it = eventFactories().begin(); it != eventFactories().end(); ++it) {
+        event = (*it)->create(eventType);
+        if (event)
+            return event.release();
+    }
     exceptionState.throwDOMException(NotSupportedError, "The provided event type ('" + eventType + "') is invalid.");
     return nullptr;
 }