Revert "Add "own" symbols support."

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 9e3da11508c030040eec6a68a24de64f7f1aa718..62e80e7a5a4094fb802195ec5c832df86b368f89 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8954,9 +8954,6 @@ class Name: public HeapObject {
   // Conversion.
   inline bool AsArrayIndex(uint32_t* index);
 
-  // Whether name can only name own properties.
-  inline bool IsOwn();
-
   DECLARE_CAST(Name)
 
   DECLARE_PRINTER(Name)
@@ -9032,10 +9029,6 @@ class Symbol: public Name {
   // [is_private]: whether this is a private symbol.
   DECL_BOOLEAN_ACCESSORS(is_private)
 
-  // [is_own]: whether this is an own symbol, that is, only used to designate
-  // own properties of objects.
-  DECL_BOOLEAN_ACCESSORS(is_own)
-
   DECLARE_CAST(Symbol)
 
   // Dispatched behavior.
@@ -9051,7 +9044,6 @@ class Symbol: public Name {
 
  private:
   static const int kPrivateBit = 0;
-  static const int kOwnBit = 1;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Symbol);
 };