Remove --harmony-tostring runtime flag

src/objects.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 "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 2445 matching lines @@
       JSFunction* constructor = JSFunction::cast(maybe_constructor);
       String* name = String::cast(constructor->shared()->name());
       if (name->length() == 0) name = constructor->shared()->inferred_name();
       if (name->length() != 0 &&
           !name->Equals(isolate->heap()->Object_string())) {
         return handle(name, isolate);
       }
     }
   }
 
-  if (FLAG_harmony_tostring) {
-    Handle<Object> maybe_tag = JSReceiver::GetDataProperty(
-        receiver, isolate->factory()->to_string_tag_symbol());
-    if (maybe_tag->IsString()) return Handle<String>::cast(maybe_tag);
-  }
+  Handle<Object> maybe_tag = JSReceiver::GetDataProperty(
+      receiver, isolate->factory()->to_string_tag_symbol());
+  if (maybe_tag->IsString()) return Handle<String>::cast(maybe_tag);
 
   PrototypeIterator iter(isolate, receiver);
   if (iter.IsAtEnd()) return handle(receiver->class_name());
   Handle<JSReceiver> start = PrototypeIterator::GetCurrent<JSReceiver>(iter);
   LookupIterator it(receiver, isolate->factory()->constructor_string(), start,
                     LookupIterator::PROTOTYPE_CHAIN_SKIP_INTERCEPTOR);
   Handle<Object> maybe_constructor = JSReceiver::GetDataProperty(&it);
   Handle<String> result = isolate->factory()->Object_string();
   if (maybe_constructor->IsJSFunction()) {
     JSFunction* constructor = JSFunction::cast(*maybe_constructor);
@@ skipping 14159 matching lines @@
 
 MaybeHandle<String> Object::ObjectProtoToString(Isolate* isolate,
                                                 Handle<Object> object) {
   if (object->IsUndefined()) return isolate->factory()->undefined_to_string();
   if (object->IsNull()) return isolate->factory()->null_to_string();
 
   Handle<JSReceiver> receiver =
       Object::ToObject(isolate, object).ToHandleChecked();
 
   Handle<String> tag;
-  if (FLAG_harmony_tostring) {
-    Handle<Object> to_string_tag;
-    ASSIGN_RETURN_ON_EXCEPTION(
-        isolate, to_string_tag,
-        JSReceiver::GetProperty(receiver,
-                                isolate->factory()->to_string_tag_symbol()),
-        String);
-    if (to_string_tag->IsString()) {
-      tag = Handle<String>::cast(to_string_tag);
-    }
+  Handle<Object> to_string_tag;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, to_string_tag,
+      JSReceiver::GetProperty(receiver,
+                              isolate->factory()->to_string_tag_symbol()),
+      String);
+  if (to_string_tag->IsString()) {
+    tag = Handle<String>::cast(to_string_tag);
   }
 
   if (tag.is_null()) {
     ASSIGN_RETURN_ON_EXCEPTION(isolate, tag,
                                JSReceiver::BuiltinStringTag(receiver), String);
   }
 
   IncrementalStringBuilder builder(isolate);
   builder.AppendCString("[object ");
   builder.AppendString(tag);
@@ skipping 3124 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8