Remove flags for ES2015 features shipped in M48

test/cctest/test-api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 24729 matching lines @@
   v8::Local<v8::Function> foo = v8::Local<v8::Function>::Cast(
       global_object->Get(env.local(), v8_str("boom")).ToLocalChecked());
 
   CHECK(foo->Call(env.local(), global_object, 0, NULL).IsEmpty());
 
   CHECK_EQ(1, nb_uncaught_exception_callback_calls);
 }
 
 
 TEST(AccessCheckedIsConcatSpreadable) {
-  i::FLAG_harmony_concat_spreadable = true;
   v8::Isolate* isolate = CcTest::isolate();
   HandleScope scope(isolate);
   LocalContext env;
 
   // Object with access check
   Local<ObjectTemplate> spreadable_template = v8::ObjectTemplate::New(isolate);
   spreadable_template->SetAccessCheckCallback(AccessBlocker);
   spreadable_template->Set(v8::Symbol::GetIsConcatSpreadable(isolate),
                            v8::Boolean::New(isolate, true));
   Local<Object> object =
@@ skipping 118 matching lines @@
   CHECK(proxy->GetTarget()->SameValue(target));
   CHECK(proxy->GetHandler()->SameValue(handler));
 
   proxy->Revoke();
   CHECK(proxy->IsProxy());
   CHECK(!target->IsProxy());
   CHECK(proxy->IsRevoked());
   CHECK(proxy->GetTarget()->SameValue(target));
   CHECK(proxy->GetHandler()->IsNull());
 }