XFA: Upgrade libpng to 1.6.20.

third_party/third_party.gyp

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'pdf_enable_xfa%': 0,  # Set to 1 by standalone.gypi in standalone builds.
   },
   'target_defaults': {
     'defines': [
@@ skipping 251 matching lines @@
         'libopenjpeg20/t1.c',
         'libopenjpeg20/t2.c',
         'libopenjpeg20/tcd.c',
         'libopenjpeg20/tgt.c',
       ],
     },
     {
       'target_name': 'fx_lpng',
       'type': 'static_library',
       'sources': [
-        'lpng_v163/png.h',
-        'lpng_v163/png.c',
-        'lpng_v163/pngerror.c',
-        'lpng_v163/pngget.c',
-        'lpng_v163/pngmem.c',
-        'lpng_v163/pngpread.c',
-        'lpng_v163/pngread.c',
-        'lpng_v163/pngrio.c',
-        'lpng_v163/pngrtran.c',
-        'lpng_v163/pngrutil.c',
-        'lpng_v163/pngset.c',
-        'lpng_v163/pngtrans.c',
-        'lpng_v163/pngwio.c',
-        'lpng_v163/pngwrite.c',
-        'lpng_v163/pngwtran.c',
-        'lpng_v163/pngwutil.c',
+        'libpng/png.c',
+        'libpng/png.h',
+        'libpng/pngconf.h',
+        'libpng/pngdebug.h',
+        'libpng/pngerror.c',
+        'libpng/pngget.c',
+        'libpng/pnginfo.h',
+        'libpng/pnglibconf.h',
+        'libpng/pngmem.c',
+        'libpng/pngpread.c',
+        'libpng/pngpriv.h',
+        'libpng/pngread.c',
+        'libpng/pngrio.c',
+        'libpng/pngrtran.c',
+        'libpng/pngrutil.c',
+        'libpng/pngset.c',
+        'libpng/pngstruct.h',
+        'libpng/pngtrans.c',
+        'libpng/pngwio.c',
+        'libpng/pngwrite.c',
+        'libpng/pngwtran.c',
+        'libpng/pngwutil.c',
       ],
     },
     {
       'target_name': 'fx_zlib',
       'type': 'static_library',
       'sources': [
         'zlib_v128/adler32.c',
         'zlib_v128/compress.c',
         'zlib_v128/crc32.c',
         'zlib_v128/deflate.c',
@@ skipping 67 matching lines @@
             'libtiff/tif_version.c',
             'libtiff/tif_warning.c',
             'libtiff/tif_write.c',
             'libtiff/tif_zip.c',
           ],
         },
       ],
     }],
   ],
 }