Populate PrototypeInfo with prototype_object value

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index d604b8b580f3219fa3fedbd4923aad0c5d6212df..8c2271d33178048644b42670d0a12fd4d3e04f37 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5775,6 +5775,9 @@ class DependentCode: public FixedArray {
 };
 
 
+class PrototypeInfo;
+
+
 // All heap objects have a Map that describes their structure.
 //  A Map contains information about:
 //  - Size information about the object
@@ -5982,6 +5985,16 @@ class Map: public HeapObject {
   // [prototype_info]: Per-prototype metadata. Aliased with transitions
   // (which prototype maps don't have).
   DECL_ACCESSORS(prototype_info, Object)
+  static Handle<PrototypeInfo> GetOrCreatePrototypeInfo(Handle<Map> map,
+                                                        Isolate* isolate);
+  // [prototype object]: points from a prototype map (which is never shared)
+  // to the object using it. Can be a Smi if the map is no longer used by a
+  // prototype object. Always use the GetPrototypeObject() getter, which zaps
+  // invalid references on the fly; the raw value is in the prototype_info.
+  static void SetPrototypeObject(Handle<Map> map,
+                                 Handle<JSObject> prototype_obj,
+                                 Isolate* isolate);
+  Object* GetPrototypeObject();
 
   Map* FindRootMap();
   Map* FindFieldOwner(int descriptor);
@@ -6553,8 +6566,9 @@ class Box : public Struct {
 // Container for metadata stored on each prototype map.
 class PrototypeInfo : public Struct {
  public:
-  // [prototype_object]: The object using the map holding this PrototypeInfo.
-  DECL_ACCESSORS(prototype_object, JSObject)
+  // [prototype_object]: The object using the map holding this PrototypeInfo,
+  // or Smi(0) if uninitialized.
+  DECL_ACCESSORS(prototype_object, Object)
   // [prototype_users]: WeakFixedArray containing maps using this prototype,
   // or Smi(0) if uninitialized.
   DECL_ACCESSORS(prototype_users, Object)