Revert of Add SkPngChunkReader.

include/core/SkPngChunkReader.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 SkPngChunkReader_DEFINED
-#define SkPngChunkReader_DEFINED
-
-#include "SkTypes.h"
-#include "SkRefCnt.h"
-
-/**
- *  SkPngChunkReader
- *
- *  Base class for optional callbacks to retrieve meta/chunk data out of a PNG
- *  encoded image as it is being decoded.
- *  Used by SkImageDecoder and SkCodec.
- */
-class SkPngChunkReader : public SkRefCnt {
-public:
-    /**
-     *  This will be called by the decoder when it sees an unknown chunk.
-     *
-     *  Use by SkCodec:
-     *  Depending on the location of the unknown chunks, this callback may be
-     *  called by
-     *      - the factory (NewFromStream/NewFromData)
-     *      - getPixels
-     *      - startScanlineDecode
-     *      - the first call to getScanlines/skipScanlines
-     *  The callback may be called from a different thread (e.g. if the SkCodec
-     *  is passed to another thread), and it may be called multiple times, if
-     *  the SkCodec is used multiple times.
-     *
-     *  @param tag Name for this type of chunk.
-     *  @param data Data to be interpreted by the subclass.
-     *  @param length Number of bytes of data in the chunk.
-     *  @return true to continue decoding, or false to indicate an error, which
-     *      will cause the decoder to not return the image.
-     */
-    virtual bool readChunk(const char tag[], const void* data, size_t length) = 0;
-};
-#endif // SkPngChunkReader_DEFINED