Enables use of the Page Visibility API, with a minor bugfix.
Enyo-DCO-1.1-Signed-off-by: Jason Robitaille <jason.robitaille@lge.com>
Merge pull request #40 from webOS-DevRel/page-visibility-api-jasonrobitaille

Enables use of the Page Visibility API, with a minor bugfix.

Reviewed-By: Ben Combee (ben.combee@lge.com)