Revert of SkOncePtr -> SkOnce

src/core/SkData.cpp

Index: src/core/SkData.cpp
diff --git a/src/core/SkData.cpp b/src/core/SkData.cpp
index ea2da3dae462c74f2bba68a9af8fba80329ea647..995a30a542470e6bd37e7f9cd08d5d6cb9ab45fc 100644
--- a/src/core/SkData.cpp
+++ b/src/core/SkData.cpp
@@ -7,7 +7,7 @@
 
 #include "SkData.h"
 #include "SkOSFile.h"
-#include "SkOnce.h"
+#include "SkOncePtr.h"
 #include "SkReadBuffer.h"
 #include "SkStream.h"
 #include "SkWriteBuffer.h"
@@ -80,12 +80,10 @@
 
 ///////////////////////////////////////////////////////////////////////////////
 
+SK_DECLARE_STATIC_ONCE_PTR(SkData, gEmpty);
 sk_sp<SkData> SkData::MakeEmpty() {
-    static SkOnce once;
-    static SkData* empty;
-
-    once([]{ empty = new SkData(nullptr, 0, nullptr, nullptr); });
-    return sk_ref_sp(empty);
+    SkData* data = SkRef(gEmpty.get([]{return new SkData(nullptr, 0, nullptr, nullptr); }));
+    return sk_sp<SkData>(data);
 }
 
 // assumes fPtr was allocated via sk_malloc