Expose IsConstructor to the C++ API

test/cctest/test-api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 11083 matching lines @@
 
 
 THREADED_TEST(FunctionRemovePrototype) {
   LocalContext context;
   v8::Isolate* isolate = context->GetIsolate();
   v8::HandleScope handle_scope(isolate);
 
   Local<v8::FunctionTemplate> t1 = v8::FunctionTemplate::New(isolate);
   t1->RemovePrototype();
   Local<v8::Function> fun = t1->GetFunction(context.local()).ToLocalChecked();
+  CHECK(!fun->IsConstructor());
   CHECK(context->Global()->Set(context.local(), v8_str("fun"), fun).FromJust());
   CHECK(!CompileRun("'prototype' in fun")
              ->BooleanValue(context.local())
              .FromJust());
 
   v8::TryCatch try_catch(isolate);
   CompileRun("new fun()");
   CHECK(try_catch.HasCaught());
 
   try_catch.Reset();
@@ skipping 13875 matching lines @@
 }
 
 TEST(PrivateForApiIsNumber) {
   LocalContext context;
   v8::Isolate* isolate = CcTest::isolate();
   v8::HandleScope scope(isolate);
 
   // Shouldn't crash.
   v8::Private::ForApi(isolate, v8_str("42"));
 }