[es6] Introduce spec compliant IsConstructor.

src/objects-debug.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/objects.h"
 
 #include "src/bootstrapper.h"
 #include "src/disasm.h"
 #include "src/disassembler.h"
 #include "src/macro-assembler.h"
 #include "src/ostreams.h"
 #include "src/regexp/jsregexp.h"
 
 namespace v8 {
 namespace internal {
 
 #ifdef VERIFY_HEAP
 
 void Object::ObjectVerify() {
   if (IsSmi()) {
     Smi::cast(this)->SmiVerify();
   } else {
     HeapObject::cast(this)->HeapObjectVerify();
   }
+  CHECK(!IsConstructor() || IsCallable());
 }
 
 
 void Object::VerifyPointer(Object* p) {
   if (p->IsHeapObject()) {
     HeapObject::VerifyHeapPointer(p);
   } else {
     CHECK(p->IsSmi());
   }
 }
 
 
 void Smi::SmiVerify() {
   CHECK(IsSmi());
   CHECK(!IsCallable());
+  CHECK(!IsConstructor());
 }
 
 
 void HeapObject::HeapObjectVerify() {
   InstanceType instance_type = map()->instance_type();
 
   if (instance_type < FIRST_NONSTRING_TYPE) {
     String::cast(this)->StringVerify();
     return;
   }
@@ skipping 1279 matching lines @@
 
   // Both are done at the same time.
   CHECK_EQ(new_it.done(), old_it.done());
 }
 
 
 #endif  // DEBUG
 
 }  // namespace internal
 }  // namespace v8