Remove unused kShortFlagsContinue.
Remove unused kShortFlagsContinue.

This will fix Chromium's clang build error.

R=tkent@chromium.org

Review URL: https://codereview.chromium.org/216263002
jgedler/ots,jgedler/ots,jgedler/ots,a19810227/ots,a19810227/ots,a19810227/ots