Enable "system-ui" generic font family

third_party/WebKit/Source/platform/fonts/android/FontCacheAndroid.cpp

 /*
  * Copyright (c) 2011 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 21 matching lines @@
 
 #include "platform/Language.h"
 #include "platform/fonts/SimpleFontData.h"
 #include "platform/fonts/FontDescription.h"
 #include "platform/fonts/FontFaceCreationParams.h"
 #include "third_party/skia/include/core/SkTypeface.h"
 #include "third_party/skia/include/ports/SkFontMgr.h"
 
 namespace blink {
 
+static AtomicString defaultFontFamily(SkFontMgr* fontManager) {
+  sk_sp<SkTypeface> typeface(
+      fontManager->legacyCreateTypeface(nullptr, SkFontStyle()));
+  SkString familyName;
+  typeface->getFamilyName(&familyName);
+  return familyName.c_str();
+}
+
+static AtomicString defaultFontFamily() {
+  if (SkFontMgr* fontManager = FontCache::fontCache()->fontManager())
+    return defaultFontFamily(fontManager);
+  sk_sp<SkFontMgr> fm(SkFontMgr::RefDefault());
+  return defaultFontFamily(fm.get());
+}
+
+// static
+const AtomicString& FontCache::systemFontFamily() {
+  DEFINE_STATIC_LOCAL(AtomicString, systemFontFamily, (defaultFontFamily()));
+  return systemFontFamily;
+}
+
 PassRefPtr<SimpleFontData> FontCache::fallbackFontForCharacter(
     const FontDescription& fontDescription,
     UChar32 c,
     const SimpleFontData*,
     FontFallbackPriority fallbackPriority) {
   sk_sp<SkFontMgr> fm(SkFontMgr::RefDefault());
   AtomicString familyName =
       getFamilyNameForCharacter(fm.get(), c, fontDescription, fallbackPriority);
   if (familyName.isEmpty())
     return getLastResortFallbackFont(fontDescription, DoNotRetain);
@@ skipping 38 matching lines @@
       // For other scripts, use the default generic family mapping logic.
       return familyName;
   }
 
   sk_sp<SkFontMgr> fm(SkFontMgr::RefDefault());
   return getFamilyNameForCharacter(fm.get(), examplerChar, fontDescription,
                                    FontFallbackPriority::Text);
 }
 
 }  // namespace blink