Make CallSite constructor inaccessible from JS

src/builtins/builtins-internal.cc

 // Copyright 2016 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.
 
 #include "src/builtins/builtins.h"
 #include "src/builtins/builtins-utils.h"
 
 #include "src/macro-assembler.h"
 
 namespace v8 {
 namespace internal {
 
 BUILTIN(Illegal) {
   UNREACHABLE();
   return isolate->heap()->undefined_value();  // Make compiler happy.
 }
 
 BUILTIN(EmptyFunction) { return isolate->heap()->undefined_value(); }
 
+BUILTIN(UnsupportedThrower) {
+  HandleScope scope(isolate);
+  THROW_NEW_ERROR_RETURN_FAILURE(isolate,
+                                 NewError(MessageTemplate::kUnsupported));
+}
+
 // -----------------------------------------------------------------------------
 // Throwers for restricted function properties and strict arguments object
 // properties
 
 BUILTIN(RestrictedFunctionPropertiesThrower) {
   HandleScope scope(isolate);
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError(MessageTemplate::kRestrictedFunctionProperties));
 }
 
 BUILTIN(RestrictedStrictArgumentsPropertiesThrower) {
   HandleScope scope(isolate);
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError(MessageTemplate::kStrictPoisonPill));
 }
 
 // -----------------------------------------------------------------------------
 // Interrupt and stack checks.
 
 void Builtins::Generate_InterruptCheck(MacroAssembler* masm) {
   masm->TailCallRuntime(Runtime::kInterrupt);
 }
 
 void Builtins::Generate_StackCheck(MacroAssembler* masm) {
   masm->TailCallRuntime(Runtime::kStackGuard);
 }
 
 }  // namespace internal
 }  // namespace v8