Set the font family for the "system-ui" generic font family on Linux

third_party/WebKit/Source/platform/fonts/mac/FontCacheMac.mm

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 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.
@@ skipping 38 matching lines @@
 // Request for public API: rdar://13803570
 @interface NSFont (WebKitSPI)
 + (NSFont*)findFontLike:(NSFont*)font forString:(NSString*)string withRange:(NSRange)range inLanguage:(id)useNil;
 + (NSFont*)findFontLike:(NSFont*)font forCharacter:(UniChar)uc inLanguage:(id)useNil;
 @end
 
 namespace blink {
 
 const char* kColorEmojiFontMac = "Apple Color Emoji";
 
+// static
+const AtomicString& FontCache::systemFontFamily()
+{
+    DEFINE_STATIC_LOCAL(AtomicString, systemFontFamilyName, ("system-ui"));

[drott, 2016/09/29 13:48:54]

Does this work on all OS X versions?

+    return systemFontFamilyName;
+}
+
 static void invalidateFontCache()
 {
     if (!isMainThread()) {
         Platform::current()->mainThread()->getWebTaskRunner()->postTask(BLINK_FROM_HERE, WTF::bind(&invalidateFontCache));
         return;
     }
     FontCache::fontCache()->invalidate();
 }
 
 static void fontCacheRegisteredFontsChangedNotificationCallback(CFNotificationCenterRef, void* observer, CFStringRef name, const void *, CFDictionaryRef)
@@ skipping 166 matching lines @@
     // When loading fails, we do not want to use the returned FontPlatformData since it will not have
     // a valid SkTypeface.
     std::unique_ptr<FontPlatformData> platformData = wrapUnique(new FontPlatformData(platformFont, size, syntheticBold, syntheticItalic, fontDescription.orientation()));
     if (!platformData->typeface()) {
         return nullptr;
     }
     return platformData;
 }
 
 } // namespace blink