Revert "Revert "[oilpan]: Make thread shutdown more robust.""

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 039942a967d4975a076a205fe34e5feb3aa66aea..f02e95c58106ce8483d4caa00cf76009632346aa 100644
--- a/Source/platform/heap/Handle.h
+++ b/Source/platform/heap/Handle.h
@@ -220,6 +220,9 @@ protected:
         , m_roots(RootsAccessor::roots())
 #endif
     {
+        // We don't support allocation of thread local Persistents while doing
+        // thread shutdown/cleanup.
+        ASSERT(!ThreadState::current()->isTerminating());
         typename RootsAccessor::Lock lock;
         ASSERT(otherref.m_roots == m_roots); // Handles must belong to the same list.
         PersistentBase* other = const_cast<PersistentBase*>(&otherref);
@@ -247,6 +250,14 @@ public:
             current->trace(visitor);
     }
 
+    int numberOfPersistents()
+    {
+        int numberOfPersistents = 0;
+        for (PersistentNode* current = m_next; current != this; current = current->m_next)
+            ++numberOfPersistents;
+        return numberOfPersistents;
+    }
+
     virtual ~PersistentAnchor()
     {
         // FIXME: oilpan: Ideally we should have no left-over persistents at this point. However currently there is a