Add a comment explaining the magic of needToStretchChildLogicalHeight
Add a comment explaining the magic of needToStretchChildLogicalHeight

R=leviw@chromium.org,ojan@chromium.org

Review URL: https://codereview.chromium.org/1116783005

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@194692 bbb929c8-8fbe-4397-9dbb-9b2b20218538

smishenk/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,XiaosongWei/blink-crosswalk,Pluto-tv/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,smishenk/blink-crosswalk,Pluto-tv/blink-crosswalk,PeterWangIntel/blink-crosswalk,smishenk/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,smishenk/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,PeterWangIntel/blink-crosswalk,XiaosongWei/blink-crosswalk,Pluto-tv/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,PeterWangIntel/blink-crosswalk,XiaosongWei/blink-crosswalk,smishenk/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Bysmyyr/blink-crosswalk,Bysmyyr/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,PeterWangIntel/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,smishenk/blink-crosswalk,PeterWangIntel/blink-crosswalk,PeterWangIntel/blink-crosswalk,XiaosongWei/blink-crosswalk,PeterWangIntel/blink-crosswalk,XiaosongWei/blink-crosswalk,smishenk/blink-crosswalk,Bysmyyr/blink-crosswalk,Pluto-tv/blink-crosswalk,Bysmyyr/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Bysmyyr/blink-crosswalk,XiaosongWei/blink-crosswalk,Bysmyyr/blink-crosswalk