URL: http://www.libpng.org/pub/png/libpng.html
Version: 1.6.16
License: libpng license
License File: LICENSE, pulled out of png.h
Description: png compression/decompression library
Local Modifications: Created pnglibconf.h from pnglibconf.h.prebuilt (just a
    rename). Pulled LICENSE into its own file.

FAQ:
Q: Why does this directory exist?
A: libpng is pulled in through DEPS, but in order to build it using ninja, we
   need to create pnglibconf.h. In https://codereview.chromium.org/930283002/,
   we originally tried creating the file as an action, but this apparently led
   to a race condition on Windows, where some builds failed to create the file
   in time for other files to include it. By checking pnglibconf.h directly
   into Skia, we eliminate the race condition.