Print out how many AllocationMementos were found during mark-sweep.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index cd651060dc83bab332ec64bc5dc2da299f09addd..6ee5b5788bf5837e213e7a01255381676ad214ad 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -7889,7 +7889,8 @@ class AllocationMemento: public Struct {
   DECLARE_VERIFIER(AllocationMemento)
 
   // Returns NULL if no AllocationMemento is available for object.
-  static AllocationMemento* FindForJSObject(JSObject* object);
+  static AllocationMemento* FindForJSObject(JSObject* object,
+                                            bool in_GC = false);
   static inline AllocationMemento* cast(Object* obj);
 
  private: