Enable "system-ui" generic font family

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

 /*
  * 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.
@@ skipping 89 matching lines @@
 
 FontPlatformData* FontCache::getFontPlatformData(
     const FontDescription& fontDescription,
     const FontFaceCreationParams& creationParams,
     bool checkingAlternateName) {
   if (!gFontPlatformDataCache) {
     gFontPlatformDataCache = new FontPlatformDataCache;
     platformInit();
   }
 
+  if (creationParams.creationType() == CreateFontByFamily) {
+#if OS(MACOSX)
+    if (creationParams.family() == FontCache::legacySystemFontFamily()) {
+      return getFontPlatformData(
+          fontDescription, FontFaceCreationParams(FontFamilyNames::system_ui),
+          true);
+    }
+#else
+    if (creationParams.family() == FontFamilyNames::system_ui) {
+      const AtomicString& actualFamily = FontCache::systemFontFamily();
+#if OS(LINUX)
+      if (actualFamily.isEmpty() || actualFamily == FontFamilyNames::system_ui)
+        return nullptr;
+#else
+      DCHECK(!actualFamily.isEmpty() &&
+             actualFamily != FontFamilyNames::system_ui);
+#endif
+      return getFontPlatformData(fontDescription,
+                                 FontFaceCreationParams(actualFamily), true);
+    }
+#endif
+  }
+
   float size = fontDescription.effectiveFontSize();
   unsigned roundedSize = size * FontCacheKey::precisionMultiplier();
   FontCacheKey key = fontDescription.cacheKey(creationParams);
 
   // Remove the font size from the cache key, and handle the font size
   // separately in the inner HashMap. So that different size of FontPlatformData
   // can share underlying SkTypeface.
   if (RuntimeEnabledFeatures::fontCacheScalingEnabled())
     key.clearFontSize();
 
@@ skipping 329 matching lines @@
   for (iter = gFallbackListShaperCache->begin();
        iter != gFallbackListShaperCache->end(); ++iter) {
     shapeResultCacheSize += iter->value->byteSize();
   }
   dump->AddScalar("size", "bytes", shapeResultCacheSize);
   memoryDump->AddSuballocation(dump->guid(),
                                WTF::Partitions::kAllocatedObjectPoolName);
 }
 
 }  // namespace blink