Bug 868066 - Check to see if RequestDecode inside PrepareImage finished decoding the image and just draw it if so. r=dholbert, a=tef+

This is a quasi-backport of bug 799335.
Bug 868530 - Unique window identifier for identity on b2g device. r=jst, a=tef+
Bug 860571 - Pings for Firefox OS. r=ferjm, a=tef+