When touch moves above/below editable area, the touch handler snaps to the beginning/end. Now it works well in Chromeos as in Android.
After this change, the snaps problem while moving the mouse also correct.

BUG=252237

NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/17834006

git-svn-id: svn://svn.chromium.org/blink/trunk@153640 bbb929c8-8fbe-4397-9dbb-9b2b20218538