Update the version of libpng used by Skia tests

The version of libpng we were using has some security vulnerabilities.
Update to a newer version - 1.6.20 (http://sourceforge.net/p/libpng/code/ci/047737496a77eeb97f9991919dac08ca3c149711/).

Update pnglibconf.h. The new version is a copy of the newer version of
the file, with our /* custom settings */ tacked onto the end. (The
custom settings are unchanged from the last version.)

Update the LICENSE. The new version is a copy of the LICENSE that
libpng now includes as a separate file.

Update the README file to reflect the change in source of the LICENSE
file.

BUG=skia:4573
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1453373003

Review URL: https://codereview.chromium.org/1453373003

3 files changed, 128 insertions, 182 deletions

diff --git a/third_party/libpng/LICENSE b/third_party/libpng/LICENSE
index ce2f3c8569..11f6ffe5db 100644
--- a/third_party/libpng/LICENSE
+++ b/third_party/libpng/LICENSE
@@ -1,172 +1,112 @@
-/*
- * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
- *
- * If you modify libpng you may insert additional notices immediately following
- * this sentence.
- *
- * This code is released under the libpng license.
- *
- * libpng versions 1.2.6, August 15, 2004, through 1.6.16, December 22, 2014, are
- * Copyright (c) 2004, 2006-2014 Glenn Randers-Pehrson, and are
- * distributed according to the same disclaimer and license as libpng-1.2.5
- * with the following individual added to the list of Contributing Authors:
- *
- *    Cosmin Truta
- *
- * libpng versions 1.0.7, July 1, 2000, through 1.2.5, October 3, 2002, are
- * Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
- * distributed according to the same disclaimer and license as libpng-1.0.6
- * with the following individuals added to the list of Contributing Authors:
- *
- *    Simon-Pierre Cadieux
- *    Eric S. Raymond
- *    Gilles Vollant
- *
- * and with the following additions to the disclaimer:
- *
- *    There is no warranty against interference with your enjoyment of the
- *    library or against infringement.  There is no warranty that our
- *    efforts or the library will fulfill any of your particular purposes
- *    or needs.  This library is provided with all faults, and the entire
- *    risk of satisfactory quality, performance, accuracy, and effort is with
- *    the user.
- *
- * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
- * Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson, and are
- * distributed according to the same disclaimer and license as libpng-0.96,
- * with the following individuals added to the list of Contributing Authors:
- *
- *    Tom Lane
- *    Glenn Randers-Pehrson
- *    Willem van Schaik
- *
- * libpng versions 0.89, June 1996, through 0.96, May 1997, are
- * Copyright (c) 1996, 1997 Andreas Dilger
- * Distributed according to the same disclaimer and license as libpng-0.88,
- * with the following individuals added to the list of Contributing Authors:
- *
- *    John Bowler
- *    Kevin Bracey
- *    Sam Bushell
- *    Magnus Holmgren
- *    Greg Roelofs
- *    Tom Tanner
- *
- * libpng versions 0.5, May 1995, through 0.88, January 1996, are
- * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
- *
- * For the purposes of this copyright and license, "Contributing Authors"
- * is defined as the following set of individuals:
- *
- *    Andreas Dilger
- *    Dave Martindale
- *    Guy Eric Schalnat
- *    Paul Schmidt
- *    Tim Wegner
- *
- * The PNG Reference Library is supplied "AS IS".  The Contributing Authors
- * and Group 42, Inc. disclaim all warranties, expressed or implied,
- * including, without limitation, the warranties of merchantability and of
- * fitness for any purpose.  The Contributing Authors and Group 42, Inc.
- * assume no liability for direct, indirect, incidental, special, exemplary,
- * or consequential damages, which may result from the use of the PNG
- * Reference Library, even if advised of the possibility of such damage.
- *
- * Permission is hereby granted to use, copy, modify, and distribute this
- * source code, or portions hereof, for any purpose, without fee, subject
- * to the following restrictions:
- *
- *   1. The origin of this source code must not be misrepresented.
- *
- *   2. Altered versions must be plainly marked as such and must not
- *      be misrepresented as being the original source.
- *
- *   3. This Copyright notice may not be removed or altered from
- *      any source or altered source distribution.
- *
- * The Contributing Authors and Group 42, Inc. specifically permit, without
- * fee, and encourage the use of this source code as a component to
- * supporting the PNG file format in commercial products.  If you use this
- * source code in a product, acknowledgment is not required but would be
- * appreciated.
- */
-
-/*
- * A "png_get_copyright" function is available, for convenient use in "about"
- * boxes and the like:
- *
- *     printf("%s", png_get_copyright(NULL));
- *
- * Also, the PNG logo (in PNG format, of course) is supplied in the
- * files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
- */
-
-/*
- * Libpng is OSI Certified Open Source Software.  OSI Certified is a
- * certification mark of the Open Source Initiative.
- */
-
-/*
- * The contributing authors would like to thank all those who helped
- * with testing, bug fixes, and patience.  This wouldn't have been
- * possible without all of you.
- *
- * Thanks to Frank J. T. Wojcik for helping with the documentation.
- */
-
-/*
- * Y2K compliance in libpng:
- * =========================
- *
- *    December 22, 2014
- *
- *    Since the PNG Development group is an ad-hoc body, we can't make
- *    an official declaration.
- *
- *    This is your unofficial assurance that libpng from version 0.71 and
- *    upward through 1.6.16 are Y2K compliant.  It is my belief that
- *    earlier versions were also Y2K compliant.
- *
- *    Libpng only has two year fields.  One is a 2-byte unsigned integer
- *    that will hold years up to 65535.  The other, which is deprecated,
- *    holds the date in text format, and will hold years up to 9999.
- *
- *    The integer is
- *        "png_uint_16 year" in png_time_struct.
- *
- *    The string is
- *        "char time_buffer[29]" in png_struct.  This is no longer used
- *    in libpng-1.6.x and will be removed from libpng-1.7.0.
- *
- *    There are seven time-related functions:
- *        png.c: png_convert_to_rfc_1123_buffer() in png.c
- *          (formerly png_convert_to_rfc_1123() prior to libpng-1.5.x and
- *          png_convert_to_rfc_1152() in error prior to libpng-0.98)
- *        png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c
- *        png_convert_from_time_t() in pngwrite.c
- *        png_get_tIME() in pngget.c
- *        png_handle_tIME() in pngrutil.c, called in pngread.c
- *        png_set_tIME() in pngset.c
- *        png_write_tIME() in pngwutil.c, called in pngwrite.c
- *
- *    All handle dates properly in a Y2K environment.  The
- *    png_convert_from_time_t() function calls gmtime() to convert from system
- *    clock time, which returns (year - 1900), which we properly convert to
- *    the full 4-digit year.  There is a possibility that libpng applications
- *    are not passing 4-digit years into the png_convert_to_rfc_1123_buffer()
- *    function, or that they are incorrectly passing only a 2-digit year
- *    instead of "year - 1900" into the png_convert_from_struct_tm() function,
- *    but this is not under our control.  The libpng documentation has always
- *    stated that it works with 4-digit years, and the APIs have been
- *    documented as such.
- *
- *    The tIME chunk itself is also Y2K compliant.  It uses a 2-byte unsigned
- *    integer to hold the year, and can hold years as large as 65535.
- *
- *    zlib, upon which libpng depends, is also Y2K compliant.  It contains
- *    no date-related code.
- *
- *       Glenn Randers-Pehrson
- *       libpng maintainer
- *       PNG Development Group
- */
+
+This copy of the libpng notices is provided for your convenience.  In case of
+any discrepancy between this copy and the notices in the file png.h that is
+included in the libpng distribution, the latter shall prevail.
+
+COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
+
+If you modify libpng you may insert additional notices immediately following
+this sentence.
+
+This code is released under the libpng license.
+
+libpng versions 1.0.7, July 1, 2000, through 1.6.19, November 12, 2015, are
+Copyright (c) 2000-2002, 2004, 2006-2015 Glenn Randers-Pehrson, are
+derived from libpng-1.0.6, and are distributed according to the same
+disclaimer and license as libpng-1.0.6 with the following individuals
+added to the list of Contributing Authors:
+
+   Simon-Pierre Cadieux
+   Eric S. Raymond
+   Mans Rullgard
+   Cosmin Truta
+   Gilles Vollant
+   James Yu
+
+and with the following additions to the disclaimer:
+
+   There is no warranty against interference with your enjoyment of the
+   library or against infringement.  There is no warranty that our
+   efforts or the library will fulfill any of your particular purposes
+   or needs.  This library is provided with all faults, and the entire
+   risk of satisfactory quality, performance, accuracy, and effort is with
+   the user.
+
+libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
+Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
+libpng-0.96, and are distributed according to the same disclaimer and
+license as libpng-0.96, with the following individuals added to the list
+of Contributing Authors:
+
+   Tom Lane
+   Glenn Randers-Pehrson
+   Willem van Schaik
+
+libpng versions 0.89, June 1996, through 0.96, May 1997, are
+Copyright (c) 1996-1997 Andreas Dilger, are derived from libpng-0.88,
+and are distributed according to the same disclaimer and license as
+libpng-0.88, with the following individuals added to the list of
+Contributing Authors:
+
+   John Bowler
+   Kevin Bracey
+   Sam Bushell
+   Magnus Holmgren
+   Greg Roelofs
+   Tom Tanner
+
+libpng versions 0.5, May 1995, through 0.88, January 1996, are
+Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
+
+For the purposes of this copyright and license, "Contributing Authors"
+is defined as the following set of individuals:
+
+   Andreas Dilger
+   Dave Martindale
+   Guy Eric Schalnat
+   Paul Schmidt
+   Tim Wegner
+
+The PNG Reference Library is supplied "AS IS".  The Contributing Authors
+and Group 42, Inc. disclaim all warranties, expressed or implied,
+including, without limitation, the warranties of merchantability and of
+fitness for any purpose.  The Contributing Authors and Group 42, Inc.
+assume no liability for direct, indirect, incidental, special, exemplary,
+or consequential damages, which may result from the use of the PNG
+Reference Library, even if advised of the possibility of such damage.
+
+Permission is hereby granted to use, copy, modify, and distribute this
+source code, or portions hereof, for any purpose, without fee, subject
+to the following restrictions:
+
+  1. The origin of this source code must not be misrepresented.
+
+  2. Altered versions must be plainly marked as such and must not
+     be misrepresented as being the original source.
+
+  3. This Copyright notice may not be removed or altered from any
+     source or altered source distribution.
+
+The Contributing Authors and Group 42, Inc. specifically permit, without
+fee, and encourage the use of this source code as a component to
+supporting the PNG file format in commercial products.  If you use this
+source code in a product, acknowledgment is not required but would be
+appreciated.
+
+END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
+
+A "png_get_copyright" function is available, for convenient use in "about"
+boxes and the like:
+
+   printf("%s", png_get_copyright(NULL));
+
+Also, the PNG logo (in PNG format, of course) is supplied in the
+files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
+
+Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
+a certification mark of the Open Source Initiative. OSI has not addressed
+the additional disclaimers inserted at version 1.0.7.
+
+Glenn Randers-Pehrson
+glennrp at users.sourceforge.net
+November 12, 2015
diff --git a/third_party/libpng/README.google b/third_party/libpng/README.google
index 841b42d82b..c40482c43e 100644
--- a/third_party/libpng/README.google
+++ b/third_party/libpng/README.google
@@ -4,8 +4,10 @@ License: libpng license
 License File: LICENSE, pulled out of png.h
 Description: png compression/decompression library
 Local Modifications: (1) Created pnglibconf.h from pnglibconf.h.prebuilt (a
-    rename with a few additional settings enabled). (2) Pulled LICENSE into
-    its own file.
+    rename with a few additional settings enabled). (2) Copied LICENSE into
+    this directory. (Originally it was pulled from png.h, but libpng has
+    now provided a separate LICENSE file for convenience, which we use
+    directly.)
 
 FAQ:
 Q: Why does this directory exist?
diff --git a/third_party/libpng/pnglibconf.h b/third_party/libpng/pnglibconf.h
index 3ba831479c..15b3530f6e 100644
--- a/third_party/libpng/pnglibconf.h
+++ b/third_party/libpng/pnglibconf.h
@@ -1,10 +1,10 @@
-/* libpng 1.6.16 STANDARD API DEFINITION */
+/* libpng 1.6.19 STANDARD API DEFINITION */
 
 /* pnglibconf.h - library build configuration */
 
-/* Libpng version 1.6.16 - December 22, 2014 */
+/* Libpng version 1.6.19 - November 12, 2015 */
 
-/* Copyright (c) 1998-2014 Glenn Randers-Pehrson */
+/* Copyright (c) 1998-2015 Glenn Randers-Pehrson */
 
 /* This code is released under the libpng license. */
 /* For conditions of distribution and use, see the disclaimer */
@@ -97,13 +97,10 @@
 #define PNG_READ_tIME_SUPPORTED
 #define PNG_READ_tRNS_SUPPORTED
 #define PNG_READ_zTXt_SUPPORTED
-/*#undef PNG_SAFE_LIMITS_SUPPORTED*/
 #define PNG_SAVE_INT_32_SUPPORTED
 #define PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SEQUENTIAL_READ_SUPPORTED
 #define PNG_SETJMP_SUPPORTED
-#define PNG_SET_CHUNK_CACHE_LIMIT_SUPPORTED
-#define PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
 #define PNG_SET_OPTION_SUPPORTED
 #define PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SET_USER_LIMITS_SUPPORTED
@@ -129,6 +126,7 @@
 #define PNG_WRITE_BGR_SUPPORTED
 #define PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
 #define PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
+#define PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
 #define PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
 #define PNG_WRITE_FILLER_SUPPORTED
 #define PNG_WRITE_FILTER_SUPPORTED
@@ -187,18 +185,24 @@
 /* end of options */
 /* settings */
 #define PNG_API_RULE 0
-#define PNG_COST_SHIFT 3
 #define PNG_DEFAULT_READ_MACROS 1
 #define PNG_GAMMA_THRESHOLD_FIXED 5000
 #define PNG_IDAT_READ_SIZE PNG_ZBUF_SIZE
 #define PNG_INFLATE_BUF_SIZE 1024
+#define PNG_LINKAGE_API extern
+#define PNG_LINKAGE_CALLBACK extern
+#define PNG_LINKAGE_DATA extern
+#define PNG_LINKAGE_FUNCTION extern
 #define PNG_MAX_GAMMA_8 11
 #define PNG_QUANTIZE_BLUE_BITS 5
 #define PNG_QUANTIZE_GREEN_BITS 5
 #define PNG_QUANTIZE_RED_BITS 5
 #define PNG_TEXT_Z_DEFAULT_COMPRESSION (-1)
 #define PNG_TEXT_Z_DEFAULT_STRATEGY 0
-#define PNG_WEIGHT_SHIFT 8
+#define PNG_USER_CHUNK_CACHE_MAX 1000
+#define PNG_USER_CHUNK_MALLOC_MAX 8000000
+#define PNG_USER_HEIGHT_MAX 1000000
+#define PNG_USER_WIDTH_MAX 1000000
 #define PNG_ZBUF_SIZE 8192
 #define PNG_ZLIB_VERNUM 0 /* unknown */
 #define PNG_Z_DEFAULT_COMPRESSION (-1)