Oilpan: Count # of collected Persistent handles and use it to estimate the live object size

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 d9a390582df49e103d7c429d6d7363c1b74ad8dc..b25f3bbc0789009772a04ecf8d53943cbcdb9614 100644
--- a/Source/platform/heap/Handle.h
+++ b/Source/platform/heap/Handle.h
@@ -212,6 +212,7 @@ private:
         ThreadState* state = ThreadStateFor<ThreadingTrait<T>::Affinity>::state();
         ASSERT(state->checkThread());
         m_persistentNode = state->persistentRegion()->allocatePersistentNode(this, TraceMethodDelegate<Persistent<T>, &Persistent<T>::trace>::trampoline);
+        state->persistentAllocated();
 #if ENABLE(ASSERT)
         m_state = state;
 #endif
@@ -224,6 +225,7 @@ private:
         // Persistent handle must be created and destructed in the same thread.
         ASSERT(m_state == state);
         state->persistentRegion()->freePersistentNode(m_persistentNode);
+        state->persistentFreed();
     }
 
     void checkPointer()
@@ -497,6 +499,7 @@ private:
         ThreadState* state = ThreadState::current();
         ASSERT(state->checkThread());
         m_persistentNode = state->persistentRegion()->allocatePersistentNode(this, TraceMethodDelegate<PersistentHeapCollectionBase<Collection>, &PersistentHeapCollectionBase<Collection>::trace>::trampoline);
+        state->persistentAllocated();
 #if ENABLE(ASSERT)
         m_state = state;
 #endif
@@ -509,6 +512,7 @@ private:
         // Persistent handle must be created and destructed in the same thread.
         ASSERT(m_state == state);
         state->persistentRegion()->freePersistentNode(m_persistentNode);
+        state->persistentFreed();
     }
 
     PersistentNode* m_persistentNode;