Implement support for USB Xbox360 controllers without a driver on Mac.

Without this patch, users have to install a driver that exposes a standard HID
device for the controller. Unfortunately, apart from the problems with
requiring users to install a driver, the only such available driver
(http://tattiebogle.net/index.php/ProjectRoot/Xbox360Controller/OsxDriver)
crashes the kernel when the controller is unplugged.

This change uses IOKit to talk directly to the Xbox controller without the need
for a driver, and exposes it through the normal HTML5 gamepad API.

BUG=232238
R=scottmg@chromium.org

Review URL: https://chromiumcodereview.appspot.com/14328036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@201717 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed