Instrument trace event into SpellChecker class
Instrument trace event into SpellChecker class

This patch introduces trace events into member functions of |SpellChecker|
related to editing function to collect spell checker execution time for
evaluating whether we need to change current spell checker integration into
editor or not.

BUG=517298
TEST=n/a; no behavior changes

Review URL: https://codereview.chromium.org/1278663003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@200141 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