[builtins] Fix context for ConstructStub calls into C++.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 8da5e92ddec8071302fa14f2ce6a490655cd031b..d28516e1413a36b920d6e44595e82f7ec4a5d6da 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -1539,8 +1539,7 @@ MaybeHandle<JSFunction> CompileString(Handle<Context> context,
 // ES6 section 18.2.1 eval (x)
 BUILTIN(GlobalEval) {
   HandleScope scope(isolate);
-  DCHECK_LE(1, args.length());
-  Handle<Object> x = args.at<Object>(1);
+  Handle<Object> x = args.atOrUndefined(isolate, 1);
   Handle<JSFunction> target = args.target();
   Handle<JSObject> target_global_proxy(target->global_proxy(), isolate);
   if (!x->IsString()) return *x;
@@ -2041,7 +2040,6 @@ BUILTIN(FunctionPrototypeBind) {
 BUILTIN(FunctionPrototypeToString) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
-
   if (receiver->IsJSBoundFunction()) {
     return *JSBoundFunction::ToString(Handle<JSBoundFunction>::cast(receiver));
   } else if (receiver->IsJSFunction()) {
@@ -2067,9 +2065,8 @@ BUILTIN(GeneratorFunctionConstructor) {
 // ES6 section 19.4.1.1 Symbol ( [ description ] ) for the [[Call]] case.
 BUILTIN(SymbolConstructor) {
   HandleScope scope(isolate);
-  DCHECK_EQ(2, args.length());
   Handle<Symbol> result = isolate->factory()->NewSymbol();
-  Handle<Object> description = args.at<Object>(1);
+  Handle<Object> description = args.atOrUndefined(isolate, 1);
   if (!description->IsUndefined()) {
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, description,
                                        Object::ToString(isolate, description));
@@ -2082,9 +2079,6 @@ BUILTIN(SymbolConstructor) {
 // ES6 section 19.4.1.1 Symbol ( [ description ] ) for the [[Construct]] case.
 BUILTIN(SymbolConstructor_ConstructStub) {
   HandleScope scope(isolate);
-  // The ConstructStub is executed in the context of the caller, so we need
-  // to enter the callee context first before raising an exception.
-  isolate->set_context(args.target()->context());
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError(MessageTemplate::kNotConstructor,
                             isolate->factory()->Symbol_string()));
@@ -2102,11 +2096,6 @@ BUILTIN(ObjectProtoToString) {
 }
 
 
-namespace {
-
-}  // namespace
-
-
 // ES6 section 26.2.1.1 Proxy ( target, handler ) for the [[Call]] case.
 BUILTIN(ProxyConstructor) {
   HandleScope scope(isolate);
@@ -2123,9 +2112,6 @@ BUILTIN(ProxyConstructor_ConstructStub) {
   DCHECK(isolate->proxy_function()->IsConstructor());
   Handle<Object> target = args.atOrUndefined(isolate, 1);
   Handle<Object> handler = args.atOrUndefined(isolate, 2);
-  // The ConstructStub is executed in the context of the caller, so we need
-  // to enter the callee context first before raising an exception.
-  isolate->set_context(args.target()->context());
   Handle<JSProxy> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result,
                                      JSProxy::New(isolate, target, handler));