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

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 d3a1cc23de41db114edbae4e6c19e368a1bde476..e124b80fffbc9d3508eb84aed57a5510831d5a64 100644
--- a/Source/platform/heap/Handle.h
+++ b/Source/platform/heap/Handle.h
@@ -948,6 +948,10 @@ public:
 
     void clear()
     {
+#if ENABLE(ASSERT)
+        if (m_keepAlive)
+            ThreadState::decrementSelfKeepAliveAllocations();
+#endif
         m_keepAlive.clear();
     }
 
@@ -958,8 +962,12 @@ private:
     void assign(Self* self)
     {
         ASSERT(!m_keepAlive || m_keepAlive->get() == self);
-        if (!m_keepAlive)
+        if (!m_keepAlive) {
             m_keepAlive = adoptPtr(new Persistent<Self>);
+#if ENABLE(ASSERT)
+            ThreadState::incrementSelfKeepAliveAllocations();
+#endif
+        }
         *m_keepAlive = self;
     }