Update libpng to version 1.2.44

      According to libpng website, this will solve the vulnerability ID CVE-2010-1205.

BUG=47633
TEST=None

Review URL: http://codereview.chromium.org/2835021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@50937 0039d316-1c4b-4281-b951-d872f2087c98