Make generators non-constructable.

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 4452 matching lines @@
     set_bit_field(bit_field() & ~(1 << kHasNonInstancePrototype));
   }
 }
 
 
 bool Map::has_non_instance_prototype() {
   return ((1 << kHasNonInstancePrototype) & bit_field()) != 0;
 }
 
 
-void Map::set_is_constructor() {
-  set_bit_field(bit_field() | (1 << kIsConstructor));
+void Map::set_is_constructor(bool value) {
+  if (value) {
+    set_bit_field(bit_field() | (1 << kIsConstructor));
+  } else {
+    set_bit_field(bit_field() & ~(1 << kIsConstructor));
+  }
 }
 
 
 bool Map::is_constructor() const {
   return ((1 << kIsConstructor) & bit_field()) != 0;
 }
 
 
 void Map::set_is_hidden_prototype() {
   set_bit_field3(IsHiddenPrototype::update(bit_field3(), true));
@@ skipping 3319 matching lines @@
 #undef WRITE_INT64_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_INL_H_