Rename SkCodec_libpng to SkPngCodec

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(const char*, size_t);
-
-    // Assume IsPng was called and returned true.
-    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;
-
-    // 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*, 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; }
-
-private:
-    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;
-
-    SkSwizzler::SrcConfig           fSrcConfig;
-    const int                       fNumberPasses;
-    int                             fBitDepth;
-
-    bool decodePalette(bool premultiply, int* ctableCount);
-    void destroyReadStruct();
-
-    typedef SkCodec INHERITED;
-};