restore extra slot in sentinal array that was removed in 3825. This extra value is read, but not acted-upon, by spanRec.init(), and so we need to have a valid address/slot allocated.
restore extra slot in sentinal array that was removed in 3825. This extra value
is read, but not acted-upon, by spanRec.init(), and so we need to have a valid
address/slot allocated.

Caught by the remoting_unittests in chrome run using ASAN.
Review URL: https://codereview.appspot.com/6176045

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia