Advance() always checks for stack overflow. If stack indeed overflowed,
current() would hold the kEndMarker. ParseOctalLiteral does not expect
this in the assertion, which causes assertion failure.

R=mvstanton@chromium.org
BUG=350865
LOG=N

Review URL: https://codereview.chromium.org/192773002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19764 ce2b1a6d-e550-0410-aec6-3dcde31c8c00