Add web audio externs contributed by edo999
Add web audio externs contributed by edo999

R=chadkillingsworth@missouristate.edu

git-svn-id: 818616af560c21f974e3119d89e3310384da871a@2031 b0f006be-c8cd-11de-a2e8-8d36a3108c74

knutwalker/google-closure-compiler,knutwalker/google-closure-compiler