Backed out 5 changesets (bug 907926, bug 911393, bug 917703) due to OSX reftest bustage during an unrelated CLOSED TREE

Backed out changeset 94a6733b01dc (bug 907926)
Backed out changeset 44108fb6f7cc (bug 917703)
Backed out changeset f2dd2a27af69 (bug 911393)
Backed out changeset fdb0d1053128 (bug 907926)
Backed out changeset b3616b786e8f (bug 907926)
Bug 842549 - Part 1. Generate trickle candidates from nICEr, with testing r=abr
Bug 842549 - Part 2: Plumb candidates up to signaling r=abr
Bug 842549 - Part 3. PC.js changes for trickle r=abr
Bug 842549 - Part 4. Small fix from ekr to disarm the trickle_cb when the ICE ctx is destroyed. r=abr