Revert of Revert of Fixing libpng transform use

src/codec/SkCodec_libpng.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodec.h"
 #include "SkColorTable.h"
 #include "SkEncodedFormat.h"
@@ skipping 26 matching lines @@
     png_structp                 fPng_ptr;
     png_infop                   fInfo_ptr;
 
     // These are stored here so they can be used both by normal decoding and scanline decoding.
     SkAutoTUnref<SkColorTable>  fColorTable;    // May be unpremul.
     SkAutoTDelete<SkSwizzler>   fSwizzler;
 
     SkSwizzler::SrcConfig       fSrcConfig;
     int                         fNumberPasses;
     bool                        fReallyHasAlpha;
+    int                         fBitDepth;
 
-    SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop);
+    SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop, int);
     ~SkPngCodec();
 
+
     // Helper to set up swizzler and color table. Also calls png_read_update_info.
     Result initializeSwizzler(const SkImageInfo& requestedInfo, void* dst,
                               size_t rowBytes, const Options&, SkPMColor*, int* ctableCount);
-    // Calls rewindIfNeeded, and returns true if the decoder can continue.
+
+    // Calls rewindIfNeeded and returns true if the decoder can continue.
     bool handleRewind();
     bool decodePalette(bool premultiply, int bitDepth, int* ctableCount);
     void finish();
     void destroyReadStruct();
 
     friend class SkPngScanlineDecoder;
     friend class SkPngInterlacedScanlineDecoder;
 
     typedef SkCodec INHERITED;
 };