[Mac] Don't flip window controls in RTL for macOS < 10.12

chrome/browser/ui/cocoa/l10n_util.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import <Cocoa/Cocoa.h>
 #include <stddef.h>
 
 #include "base/feature_list.h"
 #include "base/strings/string16.h"
 
@@ skipping 25 matching lines @@
 
 extern const base::Feature kExperimentalMacRTL;
 // Returns whether both:
 // 1) Experimental Mac RTL support is enabled via the ExperimentalMacRTL
 //    feature;
 // 2) The browser UI is in RTL mode.
 // If ExperimentalMacRTL becomes the default, this function can be replaced with
 // uses of base::i18n::IsRTL().
 bool ShouldDoExperimentalRTLLayout();
 
+// Returns true if ShouldDoExperimentalRTLLayout() is true and the OS is
+// 10.12 or above. macOS 10.12 is the first OS where the native stoplight
+// buttons are reversed in RTL, so manually reversing them in previous
+// OSes would make Chrome stick out.
+bool ShouldFlipWindowControlsInRTL();
+
 }  // namespace cocoa_l10n_util