Fix style errors in InputType.cpp.

This is a preparation to split InputType into two classes.

BUG=274205
TEST=none; no behavior changes.
R=keishi@chromium.org, yosin@chromium.org

Review URL: https://codereview.chromium.org/23279016

git-svn-id: svn://svn.chromium.org/blink/trunk@156526 bbb929c8-8fbe-4397-9dbb-9b2b20218538