Add SkCachedData and use it for SkMipMap

src/core/SkCachedData_priv.h

Index: src/core/SkCachedData_priv.h
diff --git a/src/core/SkCachedData_priv.h b/src/core/SkCachedData_priv.h
new file mode 100644
index 0000000000000000000000000000000000000000..247535ccbe6c8191d9dd7124ef2fa9cd52435ff2
--- /dev/null
+++ b/src/core/SkCachedData_priv.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCachedData_priv_DEFINED
+#define SkCachedData_priv_DEFINED
+
+#include "SkCachedData.h"
+
+class SkCachedDataOwner {
+public:
+    static void UnrefFromCache(SkCachedData* data) {
+//        data->fIsOwnedByCache = false;
+//        data->unref();
+    }
+};
+
+
+#endif