[es6] Introduce spec compliant IsConstructor.

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index e9c04c9776810203b2c849317444dd07037fd62f..19466e40a0d85def78cbf23551d84585752f7794 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -357,7 +357,7 @@ void Scope::Initialize() {
                          Variable::NORMAL, kCreatedInitialized);
     }
 
-    if (IsConciseMethod(function_kind_) || IsConstructor(function_kind_) ||
+    if (IsConciseMethod(function_kind_) || IsClassConstructor(function_kind_) ||
         IsAccessorFunction(function_kind_)) {
       variables_.Declare(this, ast_value_factory_->this_function_string(),
                          CONST, Variable::NORMAL, kCreatedInitialized);
@@ -1285,7 +1285,7 @@ ClassVariable* Scope::ClassVariableForMethod() const {
   // It needs to be investigated whether this causes any practical problems.
   if (!is_function_scope()) return nullptr;
   if (IsInObjectLiteral(function_kind_)) return nullptr;
-  if (!IsConciseMethod(function_kind_) && !IsConstructor(function_kind_) &&
+  if (!IsConciseMethod(function_kind_) && !IsClassConstructor(function_kind_) &&
       !IsAccessorFunction(function_kind_)) {
     return nullptr;
   }