[builtins] Move builtins into own files

src/builtins/builtins-proxy.cc

+// Copyright 2016 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/builtins/builtins.h"
+#include "src/builtins/builtins-utils.h"
+
+namespace v8 {
+namespace internal {
+
+// ES6 section 26.2.1.1 Proxy ( target, handler ) for the [[Call]] case.
+BUILTIN(ProxyConstructor) {
+  HandleScope scope(isolate);
+  THROW_NEW_ERROR_RETURN_FAILURE(
+      isolate,
+      NewTypeError(MessageTemplate::kConstructorNotFunction,
+                   isolate->factory()->NewStringFromAsciiChecked("Proxy")));
+}
+
+// ES6 section 26.2.1.1 Proxy ( target, handler ) for the [[Construct]] case.
+BUILTIN(ProxyConstructor_ConstructStub) {
+  HandleScope scope(isolate);
+  DCHECK(isolate->proxy_function()->IsConstructor());
+  Handle<Object> target = args.atOrUndefined(isolate, 1);
+  Handle<Object> handler = args.atOrUndefined(isolate, 2);
+  RETURN_RESULT_OR_FAILURE(isolate, JSProxy::New(isolate, target, handler));
+}
+
+}  // namespace internal
+}  // namespace v8