Clean up SkFontConfigInterface implementation.

src/ports/SkFontConfigInterface_direct_google3_factory.cpp

Index: src/ports/SkFontConfigInterface_direct_google3_factory.cpp
diff --git a/src/ports/SkFontConfigInterface_direct_google3_factory.cpp b/src/ports/SkFontConfigInterface_direct_google3_factory.cpp
index f0ac53fd8b5e62e176876690af99f8ca23b72d33..9e863d4f0b9bc3c8346ebbb339b42383f8d2b858 100644
--- a/src/ports/SkFontConfigInterface_direct_google3_factory.cpp
+++ b/src/ports/SkFontConfigInterface_direct_google3_factory.cpp
@@ -5,16 +5,12 @@
  * found in the LICENSE file.
  */
 
-/* migrated from chrome/src/skia/ext/SkFontHost_fontconfig_direct.cpp */
-
 #include "SkFontConfigInterface_direct_google3.h"
-#include "SkMutex.h"
+#include "SkOnce.h"
 
-SkFontConfigInterface* SkFontConfigInterface::GetSingletonDirectInterface(SkBaseMutex* mutex) {
-    SkAutoMutexAcquire ac(mutex);
-    static SkFontConfigInterfaceDirectGoogle3* singleton = nullptr;
-    if (singleton == nullptr) {
-        singleton = new SkFontConfigInterfaceDirectGoogle3;
-    }
+SkFontConfigInterface* SkFontConfigInterface::GetSingletonDirectInterface() {
+    static SkFontConfigInterface* singleton;
+    static SkOnce once;
+    once([]{ singleton = new SkFontConfigInterfaceDirectGoogle3(); });
     return singleton;
 }