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

third_party/WebKit/Source/platform/fonts/FontCache.h

 /*
  * Copyright (C) 2006, 2008 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2007-2008 Torch Mobile, Inc.
  *
  * 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 90 matching lines @@
     ShapeCache* getShapeCache(const FallbackListCompositeKey&);
 
     void addClient(FontCacheClient*);
 
     unsigned short generation();
     void invalidate();
 
     SkFontMgr* fontManager() { return m_fontManager.get(); }
     static void setFontManager(const sk_sp<SkFontMgr>&);
 
+    static const AtomicString& systemFontFamily();
 #if OS(WIN)
     static bool antialiasedTextEnabled() { return s_antialiasedTextEnabled; }
     static bool lcdTextEnabled() { return s_lcdTextEnabled; }
     static float deviceScaleFactor() { return s_deviceScaleFactor; }
     static void setAntialiasedTextEnabled(bool enabled) { s_antialiasedTextEnabled = enabled; }
     static void setLCDTextEnabled(bool enabled) { s_lcdTextEnabled = enabled; }
     static void setDeviceScaleFactor(float deviceScaleFactor) { s_deviceScaleFactor = deviceScaleFactor; }
     static void addSideloadedFontForTesting(SkTypeface*);
     // Functions to cache and retrieve the system font metrics.
     static void setMenuFontMetrics(const wchar_t* familyName, int32_t fontHeight);
     static void setSmallCaptionFontMetrics(const wchar_t* familyName, int32_t fontHeight);
     static void setStatusFontMetrics(const wchar_t* familyName, int32_t fontHeight);
     static int32_t menuFontHeight() { return s_menuFontHeight; }
     static const AtomicString& menuFontFamily() { return *s_smallCaptionFontFamilyName; }
     static int32_t smallCaptionFontHeight() { return s_smallCaptionFontHeight; }
     static const AtomicString& smallCaptionFontFamily() { return *s_smallCaptionFontFamilyName; }
     static int32_t statusFontHeight() { return s_statusFontHeight; }
     static const AtomicString& statusFontFamily() { return *s_statusFontFamilyName; }
     static void setUseSkiaFontFallback(bool useSkiaFontFallback) { s_useSkiaFontFallback = useSkiaFontFallback; }
+#elif OS(LINUX) || OS(ANDROID)
+    static void setSystemFontFamily(const char*);
 #endif
 
     typedef uint32_t FontFileKey;
     PassRefPtr<OpenTypeVerticalData> getVerticalData(const FontFileKey&, const FontPlatformData&);
 
     static void acceptLanguagesChanged(const String&);
 
 #if OS(ANDROID)
     static AtomicString getGenericFamilyNameForScript(const AtomicString& familyName, const FontDescription&);
 #else
@@ skipping 58 matching lines @@
     static float s_deviceScaleFactor;
     static HashMap<String, sk_sp<SkTypeface>>* s_sideloadedFonts;
     // The system font metrics cache.
     static AtomicString* s_menuFontFamilyName;
     static int32_t s_menuFontHeight;
     static AtomicString* s_smallCaptionFontFamilyName;
     static int32_t s_smallCaptionFontHeight;
     static AtomicString* s_statusFontFamilyName;
     static int32_t s_statusFontHeight;
     static bool s_useSkiaFontFallback;
+#elif OS(LINUX)
+    static AtomicString* s_systemFontFamilyName;
 #endif
 
     friend class SimpleFontData; // For fontDataFromFontPlatformData
     friend class FontFallbackList;
 };
 
 class PLATFORM_EXPORT FontCachePurgePreventer {
     USING_FAST_MALLOC(FontCachePurgePreventer);
     WTF_MAKE_NONCOPYABLE(FontCachePurgePreventer);
 public:
     FontCachePurgePreventer() { FontCache::fontCache()->disablePurging(); }
     ~FontCachePurgePreventer() { FontCache::fontCache()->enablePurging(); }
 };
 
 } // namespace blink
 
 #endif