Revert of [oilpan]: Remove support for tracing off-heap hashmaps.

Source/platform/heap/Handle.h

Index: Source/platform/heap/Handle.h
diff --git a/Source/platform/heap/Handle.h b/Source/platform/heap/Handle.h
index a1c426e0e9eb8435eb59c9fdbe00ba54d1495ea5..918a73135e39b7dbef858ae868b5a00a404fe9a0 100644
--- a/Source/platform/heap/Handle.h
+++ b/Source/platform/heap/Handle.h
@@ -850,7 +850,6 @@
 #define WillBeHeapLinkedStack blink::HeapLinkedStack
 #define PersistentHeapHashSetWillBeHeapHashSet blink::HeapHashSet
 #define PersistentHeapDequeWillBeHeapDeque blink::HeapDeque
-#define PersistentHeapVectorWillBeHeapVector blink::HeapVector
 
 template<typename T> PassRefPtrWillBeRawPtr<T> adoptRefWillBeNoop(T* ptr)
 {
@@ -971,7 +970,6 @@
 #define WillBeHeapLinkedStack WTF::LinkedStack
 #define PersistentHeapHashSetWillBeHeapHashSet blink::PersistentHeapHashSet
 #define PersistentHeapDequeWillBeHeapDeque blink::PersistentHeapDeque
-#define PersistentHeapVectorWillBeHeapVector blink::PersistentHeapVector
 
 template<typename T> PassRefPtrWillBeRawPtr<T> adoptRefWillBeNoop(T* ptr) { return adoptRef(ptr); }
 template<typename T> PassRefPtrWillBeRawPtr<T> adoptRefWillBeRefCountedGarbageCollected(T* ptr) { return adoptRef(ptr); }