ThreadWatcher - enable it in CANARY channel and updated the comments to explain why it is disabled in STABLE and UNKNOWN channels.
ThreadWatcher - enable it in CANARY channel and updated the comments to
explain why it is disabled in STABLE and UNKNOWN channels.

R=asvitkine@chromium.org
BUG=426203

Review URL: https://codereview.chromium.org/1130723005

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#329458}

chuan9/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,chuan9/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,hgl888/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,Chilledheart/chromium,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk