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 7d6170343445a74f62e5acbde4a1b463d7210edd..82166b81785f776bdb9421118444e5e7712de89f 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -140,7 +140,7 @@ 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());
     }