exo: gamepad: Send raw scancode to ARC

This CL modifies exo to send raw gamepad scancode to ARC when
ExoRawGamepadInfo is enabled. ARC can identify if it's raw scancode
by whether the gamepad was initialized by gamepad_added or

Previously, Exo was sending Web Gamepad keycode to ARC, but this will be
deprecated as a part of the effort to improve ARC Gampad compatibility.
Design doc: go/arc-improved-gamepad

TEST=manual(--enable-features=ExoRawGamepadInfo to /etc/chrome_dev.conf)

Change-Id: Ied4da69655623a243b9e1caa681212138d46918e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1612857
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661276}
4 files changed