Take over the gamepad module ownership

Scott admits he is not really familiar with what is going on here, so I am
taking the opportunity to step up. Brandon also knows this code well and it's
better to share the responsibility.

NOTRY=true

Review URL: https://codereview.chromium.org/340573003

git-svn-id: svn://svn.chromium.org/blink/trunk@176345 bbb929c8-8fbe-4397-9dbb-9b2b20218538