x11: Move XInput2 availability information out of the message pump.

BUG=302696
R=darin@chromium.org, derat@chromium.org

Review URL: https://codereview.chromium.org/52823002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233414 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233414