Change various helper classes to transition types to get CSSValue entirely onto the gc heap.

Source/core/storage/StorageEvent.cpp

Index: Source/core/storage/StorageEvent.cpp
diff --git a/Source/core/storage/StorageEvent.cpp b/Source/core/storage/StorageEvent.cpp
index ddcd7d831a57d4680d0c136d0a2ef48bfb4d4263..398877c585754183940d8b43540652a40da41b42 100644
--- a/Source/core/storage/StorageEvent.cpp
+++ b/Source/core/storage/StorageEvent.cpp
@@ -102,6 +102,10 @@ const AtomicString& StorageEvent::interfaceName() const
 
 void StorageEvent::trace(Visitor* visitor)
 {
+    // FIXME: oilpan: this code is not called as of now since Event is not on
+    // the oilpan heap anymore. We are keeping this code to avoid having to
+    // rewrite it once Event is moved back onto the oilpan heap.
+    visitor->trace(m_storageArea);
     Event::trace(visitor);
 }