Don't pause timers when app is backgrounded

Beacuse the JavaScripte timer was paused, the pause event can't send by
setTimeOut function.
Apply a patch from https://github.com/clelland/cordova-crosswalk-engine/
commit/e25e506cf815845480ae6e7a42be6cd0cd94f6bb

BUG=XWALK-2417
(cherry picked from commit f584f4106e93cdb5221c5f94d6fbff9657d73f1d)
Merge pull request #139 from huningxin/crosswalk-8

Don't pause timers when app is backgrounded