Simplify a case statement in Decimal.cpp slightly.

Handling for StateDot and StateDotDigit was identical save for a
"state = StateDotDigit;" in the StateDot case that's a no-op in the
StateDotDigit case anyway.

R=pkasting@chromium.org

Review URL: https://codereview.chromium.org/114093004

git-svn-id: svn://svn.chromium.org/blink/trunk@164071 bbb929c8-8fbe-4397-9dbb-9b2b20218538