Fix Android compile

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242661 0039d316-1c4b-4281-b951-d872f2087c98
Replace |reference_id| with |session_id| in ClearKeyCdm.

BUG=224786
R=jrummell@chromium.org

Review URL: https://codereview.chromium.org/121953002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242662 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242662