Processing for new SPDY4/HTTP2 SETTINGS frame payload format.

This lands server change 62089770 by mlavan.

BUG=345769

Review URL: https://codereview.chromium.org/183743007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254233 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254233