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

third_party/WebKit/Source/platform/fonts/linux/FontCacheLinux.cpp

Index: third_party/WebKit/Source/platform/fonts/linux/FontCacheLinux.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/linux/FontCacheLinux.cpp b/third_party/WebKit/Source/platform/fonts/linux/FontCacheLinux.cpp
index 0f732218ee065a5a3ec95177d4f15faca60f4686..5b61345d7ec8de406f84a9851bf6c822066b9fbe 100644
--- a/third_party/WebKit/Source/platform/fonts/linux/FontCacheLinux.cpp
+++ b/third_party/WebKit/Source/platform/fonts/linux/FontCacheLinux.cpp
@@ -34,6 +34,20 @@
 
 namespace blink {
 
+AtomicString* FontCache::s_systemFontFamilyName = 0;
+
+// static
+const AtomicString& FontCache::systemFontFamily()
+{
+    return *s_systemFontFamilyName;
+}
+
+// static
+void FontCache::setSystemFontFamily(const char* familyName)
+{
+    s_systemFontFamilyName = new AtomicString(familyName);
+}
+
 FontCache::FontCache()
     : m_purgePreventCount(0)
 {