Add use counters for XMLHttpRequestProgressEvent properties.

Gauge if removing these compatibility properties is feasible.

R=jochen@chromium.org
BUG=357112

Review URL: https://codereview.chromium.org/214563002

git-svn-id: svn://svn.chromium.org/blink/trunk@170198 bbb929c8-8fbe-4397-9dbb-9b2b20218538