Update libpng to 1.6.22beta

src/codec/SkPngFilters.h

Index: src/codec/SkPngFilters.h
diff --git a/src/codec/SkPngFilters.h b/src/codec/SkPngFilters.h
deleted file mode 100644
index 32708107d0da3fc7e47b8f609ea869c6388a6681..0000000000000000000000000000000000000000
--- a/src/codec/SkPngFilters.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/*
- * Copyright 2016 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkPngFilters_DEFINED
-#define SkPngFilters_DEFINED
-
-#include "png.h"
-#include "SkTypes.h"
-
-// We don't bother specializing Up...
-// it's so simple it's usually already perfectly autovectorized.
-
-// These all require bpp=3 (i.e. RGB).
-void   sk_sub3_sse2(png_row_infop, uint8_t*, const uint8_t*);
-void   sk_avg3_sse2(png_row_infop, uint8_t*, const uint8_t*);
-void sk_paeth3_sse2(png_row_infop, uint8_t*, const uint8_t*);
-
-// These all require bpp=4 (i.e. RGBA).
-void   sk_sub4_sse2(png_row_infop, uint8_t*, const uint8_t*);
-void   sk_avg4_sse2(png_row_infop, uint8_t*, const uint8_t*);
-void sk_paeth4_sse2(png_row_infop, uint8_t*, const uint8_t*);
-
-#endif//SkPngFilterOpts_DEFINED