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

Source/core/html/canvas/CanvasRenderingContext2D.cpp

Index: Source/core/html/canvas/CanvasRenderingContext2D.cpp
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.cpp b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
index 633ca4af98b4fc47f7a2d5840a5c54d5111b8e31..84a4294e2697b7ceb24dd1a81faf75eaa08f334c 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -163,7 +163,7 @@ void CanvasRenderingContext2D::restoreContext()
 void CanvasRenderingContext2D::dispatchContextLostEvent(Timer<CanvasRenderingContext2D>*)
 {
     if (contextLostRestoredEventsEnabled()) {
-        RefPtr<Event> event(Event::createCancelable(EventTypeNames::contextlost));
+        RefPtrWillBeRawPtr<Event> event = Event::createCancelable(EventTypeNames::contextlost);
         canvas()->dispatchEvent(event);
         if (event->defaultPrevented()) {
             m_contextRestorable = false;
@@ -208,7 +208,7 @@ void CanvasRenderingContext2D::dispatchContextRestoredEvent(Timer<CanvasRenderin
     reset();
     m_isContextLost = false;
     if (contextLostRestoredEventsEnabled()) {
-        RefPtr<Event> event(Event::create(EventTypeNames::contextrestored));
+        RefPtrWillBeRawPtr<Event> event(Event::create(EventTypeNames::contextrestored));
         canvas()->dispatchEvent(event);
     }
 }