Backed out changeset c2f27bb078fd (bug 857142)
Backed out changeset 7174bdf1201e (bug 857142)
Backed out changeset 04a45dec4326 (bug 898267)
Backed out changeset 31a1b6fff957 (bug 857142) for reftest failures
Bug 877700: Limit the Source region to the area of the parent layer surface. r=roc
bug 898720: Don't step over natural guards when iterating over instructions. (r=jbramley)
bug 858940: fix an additional case where we inspect the instruction stream without going through an iterator.  (r=jbramley)