Initialize seed for RNG in libjingle

Libjingle uses RNG from OpenSSL or NSS. In case of OpenSSL builds the RNG
needs to be seeded (while NSS seeds itself from /dev/urandom). Added code
to seed RNG when the remoting plugin is loaded.

Review URL: https://codereview.chromium.org/27183008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228665 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228665