Oilpan: catch some self-referential leaks (main thread.)

Source/platform/heap/PersistentNode.cpp

Index: Source/platform/heap/PersistentNode.cpp
diff --git a/Source/platform/heap/PersistentNode.cpp b/Source/platform/heap/PersistentNode.cpp
index 6271f7d6ea72c36c01868d2a242d3f18b4db3406..e5981176d5e1c8004cf903648a073a0f0fac75ae 100644
--- a/Source/platform/heap/PersistentNode.cpp
+++ b/Source/platform/heap/PersistentNode.cpp
@@ -7,6 +7,10 @@
 
 #include "platform/heap/Handle.h"
 
+#ifndef NDEBUG
+#include <stdio.h>
+#endif
+
 namespace blink {
 
 PersistentRegion::~PersistentRegion()
@@ -32,6 +36,25 @@ int PersistentRegion::numberOfPersistents()
     return persistentCount;
 }
 
+#ifndef NDEBUG
+void PersistentRegion::dumpLivePersistents()
+{
+    class Object;
+    using GCObject = GarbageCollected<Object>;
+
+    fprintf(stderr, "Live Persistent(heap object, trace method):\n");
+    for (PersistentNodeSlots* slots = m_slots; slots; slots = slots->m_next) {
+        for (int i = 0; i < PersistentNodeSlots::slotCount; ++i) {
+            if (!slots->m_slot[i].isUnused()) {
+                Persistent<GCObject>* persistent = reinterpret_cast<Persistent<GCObject>*>(slots->m_slot[i].self());
+                ASSERT(persistent);
+                fprintf(stderr, "%p => (%p, %p)\n", persistent, persistent->get(), slots->m_slot[i].traceCallback());
+            }
+        }
+    }
+}
+#endif
+
 void PersistentRegion::ensurePersistentNodeSlots(void* self, TraceCallback trace)
 {
     ASSERT(!m_freeListHead);