Fix inobject slack tracking for both subclassing and non-subclassing cases.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 2480df002e32720c6579103ec95991a0c48dadd6..d155c17d05b5bd3c28b170a6ef892d49ecbbd0fb 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -777,6 +777,9 @@ STATIC_ASSERT(ODDBALL_TYPE == Internals::kOddballType);
 STATIC_ASSERT(FOREIGN_TYPE == Internals::kForeignType);
 
 
+std::ostream& operator<<(std::ostream& os, InstanceType instance_type);
+
+
 #define FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(V) \
   V(FAST_ELEMENTS_SUB_TYPE)                   \
   V(DICTIONARY_ELEMENTS_SUB_TYPE)             \
@@ -5505,6 +5508,14 @@ class Map: public HeapObject {
   static const int kRetainingCounterStart = kSlackTrackingCounterEnd - 1;
   static const int kRetainingCounterEnd = 0;
 
+  // Starts the tracking by initializing object constructions countdown counter.
+  void StartInobjectSlackTracking();
+
+  inline bool IsInobjectSlackTrackingInProgress();
+
+  // Does the tracking step.
+  inline void InobjectSlackTrackingStep();
+
   // Completes inobject slack tracking for the transition tree starting at this
   // initial map.
   void CompleteInobjectSlackTracking();
@@ -7255,14 +7266,9 @@ class JSFunction: public JSObject {
   // counter is not zero.
   static const int kGenerousAllocationCount =
       Map::kSlackTrackingCounterStart - Map::kSlackTrackingCounterEnd + 1;
-  inline bool IsInobjectSlackTrackingInProgress();
 
-  // Starts the tracking.
-  // Initializes object constructions countdown counter in the initial map.
-  void StartInobjectSlackTracking();
-
-  // Completes the tracking.
-  void CompleteInobjectSlackTracking();
+  // Completes the tracking on initial map if it is active.
+  inline void CompleteInobjectSlackTrackingIfActive();
 
   // [literals_or_bindings]: Fixed array holding either
   // the materialized literals or the bindings of a bound function.