Property reconfiguring implemented. Tests added.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 135280125e1d52ca55182348fcf9da62178934a9..cd1b9a10af47d2b64efef4aefe79e0bb5c52157c 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5898,23 +5898,15 @@ class Map: public HeapObject {
   static void GeneralizeFieldType(Handle<Map> map, int modify_index,
                                   Representation new_representation,
                                   Handle<HeapType> new_field_type);
-  static Handle<Map> GeneralizeRepresentation(
-      Handle<Map> map,
-      int modify_index,
-      Representation new_representation,
-      Handle<HeapType> new_field_type,
-      StoreMode store_mode);
-  static Handle<Map> CopyGeneralizeAllRepresentations(
-      Handle<Map> map,
-      int modify_index,
-      StoreMode store_mode,
-      PropertyAttributes attributes,
-      const char* reason);
+  static Handle<Map> ReconfigureProperty(Handle<Map> map, int modify_index,
+                                         PropertyKind new_kind,
+                                         PropertyAttributes new_attributes,
+                                         Representation new_representation,
+                                         Handle<HeapType> new_field_type,
+                                         StoreMode store_mode);
   static Handle<Map> CopyGeneralizeAllRepresentations(
-      Handle<Map> map,
-      int modify_index,
-      StoreMode store_mode,
-      const char* reason);
+      Handle<Map> map, int modify_index, StoreMode store_mode,
+      PropertyKind kind, PropertyAttributes attributes, const char* reason);
 
   static Handle<Map> PrepareForDataProperty(Handle<Map> old_map,
                                             int descriptor_number,
@@ -6142,8 +6134,10 @@ class Map: public HeapObject {
   static Handle<Map> TransitionToAccessorProperty(
       Handle<Map> map, Handle<Name> name, AccessorComponent component,
       Handle<Object> accessor, PropertyAttributes attributes);
-  static Handle<Map> ReconfigureDataProperty(Handle<Map> map, int descriptor,
-                                             PropertyAttributes attributes);
+  static Handle<Map> ReconfigureExistingProperty(Handle<Map> map,
+                                                 int descriptor,
+                                                 PropertyKind kind,
+                                                 PropertyAttributes attributes);
 
   inline void AppendDescriptor(Descriptor* desc);
 
@@ -6428,6 +6422,9 @@ class Map: public HeapObject {
                                            Descriptor* descriptor,
                                            int index,
                                            TransitionFlag flag);
+  static MUST_USE_RESULT MaybeHandle<Map> TryReconfigureExistingProperty(
+      Handle<Map> map, int descriptor, PropertyKind kind,
+      PropertyAttributes attributes, const char** reason);
 
   static Handle<Map> CopyNormalized(Handle<Map> map,
                                     PropertyNormalizationMode mode);
@@ -6461,6 +6458,8 @@ class Map: public HeapObject {
                        Representation new_representation,
                        Handle<HeapType> new_type);
 
+  void PrintReconfiguration(FILE* file, int modify_index, PropertyKind kind,
+                            PropertyAttributes attributes);
   void PrintGeneralization(FILE* file,
                            const char* reason,
                            int modify_index,
@@ -6472,6 +6471,10 @@ class Map: public HeapObject {
                            HeapType* old_field_type,
                            HeapType* new_field_type);
 
+#ifdef OBJECT_PRINT
+  void PrintPrototypeTransitions(std::ostream& os);  // NOLINT
+#endif
+
   static inline void SetPrototypeTransitions(
       Handle<Map> map,
       Handle<FixedArray> prototype_transitions);
@@ -10495,6 +10498,14 @@ class AccessorPair: public Struct {
     if (!setter->IsNull()) set_setter(setter);
   }
 
+  bool Equals(AccessorPair* pair) {
+    return (this == pair) || pair->Equals(getter(), setter());
+  }
+
+  bool Equals(Object* getter_value, Object* setter_value) {
+    return (getter() == getter_value) && (setter() == setter_value);
+  }
+
   bool ContainsAccessor() {
     return IsJSAccessor(getter()) || IsJSAccessor(setter());
   }