Support RGBA/BGRA swizzles using SkEncodedInfo

src/codec/SkPngCodec.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"
@@ skipping 28 matching lines @@
     SkSampler* getSampler(bool createIfNecessary) override {
         SkASSERT(fSwizzler);
         return fSwizzler;
     }
 
     SkPngCodec(const SkEncodedInfo&, SkStream*, SkPngChunkReader*, png_structp, png_infop, int, int,
                sk_sp<SkColorSpace>);
 
     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);
+    bool decodePalette(bool premultiply, SkColorType dstColorType, int* ctableCount);
     void destroyReadStruct();
 
     typedef SkCodec INHERITED;
 };