Add support for API accessors that prohibit overwriting by accessors...

src/objects-inl.h

Index: src/objects-inl.h
===================================================================
--- src/objects-inl.h	(revision 654)
+++ src/objects-inl.h	(working copy)
@@ -1677,6 +1677,20 @@
 }
 
 
+void Map::set_is_access_check_needed(bool access_check_needed) {
+  if (access_check_needed) {
+    set_bit_field(bit_field() | (1 << kIsAccessCheckNeeded));
+  } else {
+    set_bit_field(bit_field() & ~(1 << kIsAccessCheckNeeded));
+  }
+}
+
+
+bool Map::is_access_check_needed() {
+  return ((1 << kIsAccessCheckNeeded) & bit_field()) != 0;
+}
+
+
 Code::Flags Code::flags() {
   return static_cast<Flags>(READ_INT_FIELD(this, kFlagsOffset));
 }
@@ -2298,6 +2312,16 @@
 }
 
 
+bool AccessorInfo::prohibits_overwriting() {
+  return BooleanBit::get(flag(), kProhibitsOverwritingBit);
+}
+
+
+void AccessorInfo::set_prohibits_overwriting(bool value) {
+  set_flag(BooleanBit::set(flag(), kProhibitsOverwritingBit, value));
+}
+
+
 PropertyAttributes AccessorInfo::property_attributes() {
   return AttributesField::decode(static_cast<uint32_t>(flag()->value()));
 }