Add subsetting to SkScaledCodec

src/codec/SkCodec_libpng.h

Index: src/codec/SkCodec_libpng.h
diff --git a/src/codec/SkCodec_libpng.h b/src/codec/SkCodec_libpng.h
index c24995946334b162b28d2e826d826052dd926da3..dd66b5651eb1b59ce5aa771ddefd9b2f5751e4b2 100644
--- a/src/codec/SkCodec_libpng.h
+++ b/src/codec/SkCodec_libpng.h
@@ -18,7 +18,6 @@
 #endif
 #include "png.h"
 
-class SkScanlineDecoder;
 class SkStream;
 
 class SkPngCodec : public SkCodec {
@@ -27,7 +26,6 @@ public:
 
     // Assume IsPng was called and returned true.
     static SkCodec* NewFromStream(SkStream*);
-    static SkScanlineDecoder* NewSDFromStream(SkStream*);
 
     virtual ~SkPngCodec();
 
@@ -41,7 +39,7 @@ protected:
 
     // Helper to set up swizzler and color table. Also calls png_read_update_info.
     Result initializeSwizzler(const SkImageInfo& requestedInfo, const Options&,
-                              SkPMColor*, int* ctableCount);
+                              SkPMColor*, int* ctableCount, int subsetLeft, int subsetWidth);
     SkSampler* getSampler(bool createIfNecessary) override { return fSwizzler; }
 
     SkPngCodec(const SkImageInfo&, SkStream*, png_structp, png_infop, int, int);
@@ -75,7 +73,6 @@ private:
     SkSwizzler::SrcConfig       fSrcConfig;
     const int                   fNumberPasses;
     int                         fBitDepth;
-
     AlphaState                  fAlphaState;
 
     bool decodePalette(bool premultiply, int* ctableCount);