Oilpan: have WebPerformance use transition types.

Source/web/WebPerformance.cpp

Index: Source/web/WebPerformance.cpp
diff --git a/Source/web/WebPerformance.cpp b/Source/web/WebPerformance.cpp
index 8b841e730a9e726fea3afd29cbebb6757bca4f18..1d0888126546f254c584d4020bef4143f676ff9d 100644
--- a/Source/web/WebPerformance.cpp
+++ b/Source/web/WebPerformance.cpp
@@ -168,20 +168,15 @@ double WebPerformance::loadEventEnd() const
     return millisecondsToSeconds(m_private->timing()->loadEventEnd());
 }
 
-WebPerformance::WebPerformance(const PassRefPtr<Performance>& performance)
+WebPerformance::WebPerformance(const PassRefPtrWillBeRawPtr<Performance>& performance)
     : m_private(performance)
 {
 }
 
-WebPerformance& WebPerformance::operator=(const PassRefPtr<Performance>& performance)
+WebPerformance& WebPerformance::operator=(const PassRefPtrWillBeRawPtr<Performance>& performance)
 {
     m_private = performance;
     return *this;
 }
 
-WebPerformance::operator PassRefPtr<Performance>() const
-{
-    return m_private.get();
-}
-
 } // namespace blink