[proxies] Implement [[Delete]].

src/builtins.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/builtins.h"
 
 #include "src/api.h"
 #include "src/api-natives.h"
 #include "src/arguments.h"
 #include "src/base/once.h"
@@ skipping 1482 matching lines @@
     THROW_NEW_ERROR_RETURN_FAILURE(
         isolate, NewTypeError(MessageTemplate::kCalledOnNonObject,
                               isolate->factory()->NewStringFromAsciiChecked(
                                   "Reflect.deleteProperty")));
   }
 
   Handle<Name> name;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, name,
                                      Object::ToName(isolate, key));
 
-  Handle<Object> result;
-  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
-      isolate, result, JSReceiver::DeletePropertyOrElement(
-                           Handle<JSReceiver>::cast(target), name));
-
-  return *result;
+  Maybe<bool> result = JSReceiver::DeletePropertyOrElement(
+      Handle<JSReceiver>::cast(target), name, SLOPPY);
+  MAYBE_RETURN(result, isolate->heap()->exception());
+  return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
 
 // ES6 section 26.1.6 Reflect.get
 BUILTIN(ReflectGet) {
   HandleScope scope(isolate);
   Handle<Object> undef = isolate->factory()->undefined_value();
   Handle<Object> target = args.length() > 1 ? args.at<Object>(1) : undef;
   Handle<Object> key = args.length() > 2 ? args.at<Object>(2) : undef;
   Handle<Object> receiver = args.length() > 3 ? args.at<Object>(3) : target;
@@ skipping 883 matching lines @@
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 }  // namespace internal
 }  // namespace v8