Add SkPngChunkReader.

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 "SkPngChunkReader.h"
 #include "SkEncodedFormat.h"
 #include "SkImageInfo.h"
 #include "SkRefCnt.h"
 #include "SkSwizzler.h"
 
 #include "png.h"
 
 class SkStream;
 
 class SkPngCodec : public SkCodec {
 public:
     static bool IsPng(SkStream*);
 
     // Assume IsPng was called and returned true.
-    static SkCodec* NewFromStream(SkStream*);
+    static SkCodec* NewFromStream(SkStream*, SkPngChunkReader* = NULL);
 
     virtual ~SkPngCodec();
 
 protected:
     Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&, SkPMColor*, int*, int*)
             override;
     SkEncodedFormat onGetEncodedFormat() const override { return kPNG_SkEncodedFormat; }
     bool onRewind() override;
     uint32_t onGetFillValue(SkColorType colorType, SkAlphaType alphaType) const override;
     bool onReallyHasAlpha() const final;
 
     // Helper to set up swizzler and color table. Also calls png_read_update_info.
     Result initializeSwizzler(const SkImageInfo& requestedInfo, const Options&,
                               SkPMColor*, int* ctableCount);
     SkSampler* getSampler(bool createIfNecessary) override {
         SkASSERT(fSwizzler);
         return fSwizzler;
     }
 
-    SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop, int, int);
+    SkPngCodec(const SkImageInfo&, SkStream*, SkPngChunkReader*, png_structp, png_infop, int, int);
 
     png_structp png_ptr() { return fPng_ptr; }
     SkSwizzler* swizzler() { return fSwizzler; }
     SkSwizzler::SrcConfig srcConfig() const { return fSrcConfig; }
     int numberPasses() const { return fNumberPasses; }
 
     enum AlphaState {
         // This class has done no decoding, or threw away its knowledge (in
         // scanline decodes).
         kUnknown_AlphaState,
         // This class found the image (possibly partial, in the case of a
         // scanline decode) to be opaque.
         kOpaque_AlphaState,
         // Ths class found the image to have alpha.
         kHasAlpha_AlphaState,
     };
 
     virtual AlphaState alphaInScanlineDecode() const = 0;
 
 private:
-    png_structp                 fPng_ptr;
-    png_infop                   fInfo_ptr;
+    SkAutoTUnref<SkPngChunkReader>  fPngChunkReader;
+    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;
+    SkAutoTUnref<SkColorTable>      fColorTable;    // May be unpremul.
+    SkAutoTDelete<SkSwizzler>       fSwizzler;
 
-    SkSwizzler::SrcConfig       fSrcConfig;
-    const int                   fNumberPasses;
-    int                         fBitDepth;
-    AlphaState                  fAlphaState;
+    SkSwizzler::SrcConfig           fSrcConfig;
+    const int                       fNumberPasses;
+    int                             fBitDepth;
+    AlphaState                      fAlphaState;
 
     bool decodePalette(bool premultiply, int* ctableCount);
     void destroyReadStruct();
 
     typedef SkCodec INHERITED;
 };