Add SkPngChunkReader.

include/codec/SkCodec.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.
  */
 
 #ifndef SkCodec_DEFINED
 #define SkCodec_DEFINED
 
 #include "../private/SkTemplates.h"
 #include "SkColor.h"
 #include "SkEncodedFormat.h"
 #include "SkImageInfo.h"
 #include "SkSize.h"
 #include "SkStream.h"
 #include "SkTypes.h"
 
 class SkData;
+class SkPngChunkReader;
 class SkSampler;
 
 /**
  *  Abstraction layer directly on top of an image codec.
  */
 class SkCodec : SkNoncopyable {
 public:
     /**
      *  If this stream represents an encoded image that we know how to decode,
      *  return an SkCodec that can decode it. Otherwise return NULL.
      *
+     *  If SkPngChunkReader is not NULL, take a ref and pass it to libpng if
+     *  the image is a png.
+     *
      *  If NULL is returned, the stream is deleted immediately. Otherwise, the
      *  SkCodec takes ownership of it, and will delete it when done with it.
      */
-    static SkCodec* NewFromStream(SkStream*);
+    static SkCodec* NewFromStream(SkStream*, SkPngChunkReader* = NULL);
 
     /**
      *  If this data represents an encoded image that we know how to decode,
      *  return an SkCodec that can decode it. Otherwise return NULL.
      *
+     *  If SkPngChunkReader is not NULL, take a ref and pass it to libpng if
+     *  the image is a png.
+     *
      *  Will take a ref if it returns a codec, else will not affect the data.
      */
-    static SkCodec* NewFromData(SkData*);
+    static SkCodec* NewFromData(SkData*, SkPngChunkReader* = NULL);
 
     virtual ~SkCodec();
 
     /**
      *  Return the ImageInfo associated with this codec.
      */
     const SkImageInfo& getInfo() const { return fSrcInfo; }
 
     /**
      *  Return a size that approximately supports the desired scale factor.
@@ skipping 527 matching lines @@
      *  May create a sampler, if one is not currently being used. Otherwise, does
      *  not affect ownership.
      *
      *  Only valid during scanline decoding.
      */
     virtual SkSampler* getSampler(bool /*createIfNecessary*/) { return nullptr; }
 
     friend class SkSampledCodec;
 };
 #endif // SkCodec_DEFINED