Remove always-on --harmony-rest-parameters flag

test/cctest/compiler/test-run-jsobjects.cc

 // Copyright 2015 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 "test/cctest/compiler/function-tester.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
@@ skipping 17 matching lines @@
   T.Call(T.Val(19), T.Val(23), T.Val(42), T.Val(65)).ToHandle(&arguments);
   CHECK(arguments->IsJSObject() && !arguments->IsJSArray());
   CHECK(!JSObject::cast(*arguments)->HasSloppyArgumentsElements());
   Handle<String> l = T.isolate->factory()->length_string();
   Handle<Object> length = JSObject::GetProperty(arguments, l).ToHandleChecked();
   CHECK_EQ(4, length->Number());
 }
 
 
 TEST(ArgumentsRest) {
-  FLAG_harmony_rest_parameters = true;
   FunctionTester T("(function(a, ...args) { return args; })");
 
   Handle<Object> arguments;
   T.Call(T.Val(19), T.Val(23), T.Val(42), T.Val(65)).ToHandle(&arguments);
   CHECK(arguments->IsJSObject() && arguments->IsJSArray());
   CHECK(!JSObject::cast(*arguments)->HasSloppyArgumentsElements());
   Handle<String> l = T.isolate->factory()->length_string();
   Handle<Object> length = JSObject::GetProperty(arguments, l).ToHandleChecked();
   CHECK_EQ(3, length->Number());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8