Enable "system-ui" generic font family

third_party/WebKit/Source/platform/fonts/mac/FontFamilyMatcherMac.h

 /*
  * Copyright (C) 2006, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 11 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef FontFamilyMatcherMac_h
 #define FontFamilyMatcherMac_h
 
 #include "platform/PlatformExport.h"
 #include "platform/fonts/FontTraits.h"
+#include "wtf/Forward.h"
 #include <AppKit/NSFontManager.h>
 
 namespace blink {
 
-PLATFORM_EXPORT NSFont* MatchNSFontFamily(NSString* desiredFamily,
+PLATFORM_EXPORT NSFont* MatchNSFontFamily(const AtomicString& desiredFamily,
                                           NSFontTraitMask desiredTraits,
                                           FontWeight desiredWeight,
                                           float size);
 
 // Converts a blink::FontWeight to an AppKit font weight.
 int toAppKitFontWeight(FontWeight);
 }
 
 #endif  // FontFamilyMatcherMac_h