Keyboard events with keypad had wrong keycodes on ozone.

Ozone is generating virtual keys not like Windows and X11 are generating
them. The removal of some code undercovered the issue. Add back some
of the partial conversion code (numpad conversions only) to address
the issue for the users. Whether numpad keys are "located" or not
needs to be re-evaluated and all platforms made consistent.
Documentation claims that numpad events are located but the
platforms generate them to be consistent with windows.

Ozone seemed to be the only platform that didn't generate
them. Ideally the fix should be in the
xkb_keyboard_layout_engine.cc part of ozone but for
simplicity sake and that this needs to be backported to M48; restore some of
https://codereview.chromium.org/1308063007 CL with respect to rewrite numpads based events.

BUG=570388

Review URL: https://codereview.chromium.org/1550953002

Cr-Commit-Position: refs/heads/master@{#367418}
3 files changed