Changes the type for PING id from uint32 to uint64.

Required for HTTP2.

This lands server change 60786018 by birenroy.

Minor type updates to QUIC/SpdySession & friends were also required.

Review URL: https://codereview.chromium.org/154353003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250767 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250767