Use scoped_ptr instead of raw pointer to store SpdyFramer

BUG=none
R=yhirano@chromium.org, rch@chromium.org

Review URL: https://codereview.chromium.org/175593004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253001 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253001