Allow SkAndroidCodec to use 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
 
@@ skipping 11 matching lines @@
 
 /**
  *  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 the SkPngChunkReader is not NULL then:
+     *      If the image is not a PNG, the SkPngChunkReader will be ignored.
+     *      If the image is a PNG, the SkPngChunkReader will be reffed.
+     *      If the PNG has unknown chunks, the SkPngChunkReader will be used
+     *      to handle these chunks.  SkPngChunkReader will be called to read
+     *      any unknown chunk at any point during the creation of the codec
+     *      or the decode.  Note that if SkPngChunkReader fails to read a
+     *      chunk, this could result in a failure to create the codec or a
+     *      failure to decode the image.
+     *      If the PNG does not contain unknown chunks, the SkPngChunkReader
+     *      will not be used or modified.
      *
      *  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*, 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.
+     *  If the SkPngChunkReader is not NULL then:
+     *      If the image is not a PNG, the SkPngChunkReader will be ignored.
+     *      If the image is a PNG, the SkPngChunkReader will be reffed.
+     *      If the PNG has unknown chunks, the SkPngChunkReader will be used
+     *      to handle these chunks.  SkPngChunkReader will be called to read
+     *      any unknown chunk at any point during the creation of the codec
+     *      or the decode.  Note that if SkPngChunkReader fails to read a
+     *      chunk, this could result in a failure to create the codec or a
+     *      failure to decode the image.
+     *      If the PNG does not contain unknown chunks, the SkPngChunkReader
+     *      will not be used or modified.
      *
      *  Will take a ref if it returns a codec, else will not affect the data.
      */
     static SkCodec* NewFromData(SkData*, SkPngChunkReader* = NULL);
 
     virtual ~SkCodec();
 
     /**
      *  Return the ImageInfo associated with this codec.
      */
@@ skipping 531 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