Remove dependencies on Android's forked decoder libraries

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 34 matching lines @@
 #define DEFAULT_FOR_SUPPRESS_PNG_IMAGE_DECODER_WARNINGS false
 #else  // !defined(SK_DEBUG)
 #define DEFAULT_FOR_SUPPRESS_PNG_IMAGE_DECODER_WARNINGS true
 #endif  // defined(SK_DEBUG)
 SK_CONF_DECLARE(bool, c_suppressPNGImageDecoderWarnings,
                 "images.png.suppressDecoderWarnings",
                 DEFAULT_FOR_SUPPRESS_PNG_IMAGE_DECODER_WARNINGS,
                 "Suppress most PNG warnings when calling image decode "
                 "functions.");
 
-#if defined(SK_BUILD_FOR_ANDROID) && !defined(SK_PNG_NO_INDEX_SUPPORTED)
-#define SK_PNG_INDEX_SUPPORTED
-#endif
-
 class SkPNGImageIndex {
 public:
     // Takes ownership of stream.
     SkPNGImageIndex(SkStreamRewindable* stream, png_structp png_ptr, png_infop info_ptr)
         : fStream(stream)
         , fPng_ptr(png_ptr)
         , fInfo_ptr(info_ptr)
         , fColorType(kUnknown_SkColorType) {
         SkASSERT(stream != nullptr);
     }
@@ skipping 1214 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? new SkPNGImageEncoder : nullptr;
 }
 
 static SkImageDecoder_DecodeReg gDReg(sk_libpng_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_png);
 static SkImageEncoder_EncodeReg gEReg(sk_libpng_efactory);