Fix build following r198658.
Fix build following r198658.

Reintroduce the use of ASSERT_UNUSED() in
CharacterIterator{Algorithm}:range() that r198658 dropped. It is needed.

TBR=oilpan-reviews,yosin@chromium.org
BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/1227413004

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@198737 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk