tree 4364035e90fc28db226d329b636ce5ac19ca51b7
parent 4ed187a0103e86c9c1cc413d4ef67826f40ff138
author scroggo <scroggo@chromium.org> 1455892387 -0800
committer Commit bot <commit-bot@chromium.org> 1455892387 -0800

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