Add two new histograms for the QUIC error code reported when stream was reset.

Net.QuicSession.RstStreamErrorCodeClient
Net.QuicSession.RstStreamErrorCodeServer

R=jar@chromium.org

Review URL: https://codereview.chromium.org/27740006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229466 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229466