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

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index 146ebda32f4b331805c778db26779e4473071532..fd7edfee1d5308ada92a30c9ef6994b87cd545da 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -139,7 +139,7 @@ public:
         if (!horizontalLayoutOverflowChanged && !verticalLayoutOverflowChanged)
             return;
 
-        RefPtr<OverflowEvent> event = OverflowEvent::create(horizontalLayoutOverflowChanged, hasHorizontalLayoutOverflow, verticalLayoutOverflowChanged, hasVerticalLayoutOverflow);
+        RefPtrWillBeRawPtr<OverflowEvent> event = OverflowEvent::create(horizontalLayoutOverflowChanged, hasHorizontalLayoutOverflow, verticalLayoutOverflowChanged, hasVerticalLayoutOverflow);
         event->setTarget(m_block->node());
         m_block->document().enqueueAnimationFrameEvent(event.release());
     }