Add SkPngChunkReader.

src/images/SkImageDecoder_libpng.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageDecoder.h"
 #include "SkImageEncoder.h"
 #include "SkColor.h"
@@ skipping 125 matching lines @@
     SkStreamRewindable* sk_stream = (SkStreamRewindable*) png_get_io_ptr(png_ptr);
     if (!sk_stream->rewind()) {
         png_error(png_ptr, "Failed to rewind stream!");
     }
     (void)sk_stream->skip(offset);
 }
 #endif
 
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
 static int sk_read_user_chunk(png_structp png_ptr, png_unknown_chunkp chunk) {
-    SkImageDecoder::Peeker* peeker =
-                    (SkImageDecoder::Peeker*)png_get_user_chunk_ptr(png_ptr);
-    // peek() returning true means continue decoding
-    return peeker->peek((const char*)chunk->name, chunk->data, chunk->size) ?
+    SkChunkReader* peeker = (SkChunkReader*)png_get_user_chunk_ptr(png_ptr);
+    // readChunk() returning true means continue decoding
+    return peeker->readChunk((const char*)chunk->name, chunk->data, chunk->size) ?
             1 : -1;
 }
 #endif
 
 static void sk_error_fn(png_structp png_ptr, png_const_charp msg) {
     SkDEBUGF(("------ png error %s\n", msg));
     longjmp(png_jmpbuf(png_ptr), 1);
 }
 
 static void skip_src_rows(png_structp png_ptr, uint8_t storage[], int count) {
@@ skipping 1120 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? SkNEW(SkPNGImageEncoder) : NULL;
 }
 
 static SkImageDecoder_DecodeReg gDReg(sk_libpng_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_png);
 static SkImageEncoder_EncodeReg gEReg(sk_libpng_efactory);