Use C++11 range-based loop in core/events

Improves code readabilty.
Also use >> for > > in template

BUG=none
TEST=no layout test failures

Review URL: https://codereview.chromium.org/637223008

git-svn-id: svn://svn.chromium.org/blink/trunk@183891 bbb929c8-8fbe-4397-9dbb-9b2b20218538