Oilpan: Replace most of RefPtrs for Event objects with oilpan's transition types

Source/core/page/EventSource.cpp

Index: Source/core/page/EventSource.cpp
diff --git a/Source/core/page/EventSource.cpp b/Source/core/page/EventSource.cpp
index 5d51d016f8335dd230c17cbd1cfeb485fca5d25f..f76f2fc675e949bf2b76ca21acb82703fd04da16 100644
--- a/Source/core/page/EventSource.cpp
+++ b/Source/core/page/EventSource.cpp
@@ -424,9 +424,9 @@ void EventSource::stop()
     close();
 }
 
-PassRefPtr<MessageEvent> EventSource::createMessageEvent()
+PassRefPtrWillBeRawPtr<MessageEvent> EventSource::createMessageEvent()
 {
-    RefPtr<MessageEvent> event = MessageEvent::create();
+    RefPtrWillBeRawPtr<MessageEvent> event = MessageEvent::create();
     event->initMessageEvent(m_eventName.isEmpty() ? EventTypeNames::message : m_eventName, false, false, SerializedScriptValue::create(String(m_data)), m_eventStreamOrigin, m_lastEventId, 0, nullptr);
     m_data.clear();
     return event.release();