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

third_party/WebKit/public/web/linux/WebFontRendering.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 14 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY 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 WebFontRendering_h
 #define WebFontRendering_h
 
 #include "../../platform/WebCommon.h"
+#include "../../platform/WebString.h"
 #include <SkFontMgr.h>
 #include <SkPaint.h>
 
 namespace blink {
 
 class WebFontRendering {
  public:
   // Set global font renderering preferences.
 
   BLINK_EXPORT static void setSkiaFontManager(SkFontMgr*);
   BLINK_EXPORT static void setHinting(SkPaint::Hinting);
   BLINK_EXPORT static void setAutoHint(bool);
   BLINK_EXPORT static void setUseBitmaps(bool);
   BLINK_EXPORT static void setAntiAlias(bool);
   BLINK_EXPORT static void setSubpixelRendering(bool);
   BLINK_EXPORT static void setSubpixelPositioning(bool);
   BLINK_EXPORT static void setDefaultFontSize(int);
+  BLINK_EXPORT static void setSystemFontFamily(const WebString&);
 };
 
 }  // namespace blink
 
 #endif