Implement chrome.runtime.restart for cros kiosk app.

This allows an app running in ChromeOS kiosk mode to restart the device.

BUG=287727

Review URL: https://codereview.chromium.org/25944003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227474 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227474