[es6] Introduce spec compliant IsConstructor.

src/accessors.cc

 // 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.
 
 #include "src/accessors.h"
 
 #include "src/api.h"
 #include "src/contexts.h"
 #include "src/deoptimizer.h"
 #include "src/execution.h"
@@ skipping 911 matching lines @@
         function, "update", isolate->factory()->prototype_string(), old_value);
     if (result.is_null()) return MaybeHandle<Object>();
   }
 
   return function;
 }
 
 
 MaybeHandle<Object> Accessors::FunctionSetPrototype(Handle<JSFunction> function,
                                                     Handle<Object> prototype) {
-  DCHECK(function->should_have_prototype());
+  DCHECK(function->IsConstructor());
   Isolate* isolate = function->GetIsolate();
   return SetFunctionPrototype(isolate, function, prototype);
 }
 
 
 void Accessors::FunctionPrototypeGetter(
     v8::Local<v8::Name> name,
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(info.GetIsolate());
   HandleScope scope(isolate);
@@ skipping 559 matching lines @@
   Handle<Object> getter = v8::FromCData(isolate, &ModuleGetExport);
   Handle<Object> setter = v8::FromCData(isolate, &ModuleSetExport);
   info->set_getter(*getter);
   if (!(attributes & ReadOnly)) info->set_setter(*setter);
   return info;
 }
 
 
 }  // namespace internal
 }  // namespace v8