Avoid more temporary ranges in connection with various TextIterators.

Rename the range method to createRange and remove it from the classes
where we have gotten rid of all uses.

R=yosin@chromium.org
BUG=388681

Review URL: https://codereview.chromium.org/560333002

git-svn-id: svn://svn.chromium.org/blink/trunk@181974 bbb929c8-8fbe-4397-9dbb-9b2b20218538