Backout changesets 8d69a81abff9:6c2e3ea6afa6 for M2 timeouts and crashtest, reftest leaks.
Merge backout.
Bug 859817 - Introduce already_AddRefed.downcast(); r=ehsan
Bug 859817 - Make NS_NewAtom return already_AddRefed; r=bz
Bug 859817 - Remove implicit conversions from raw pointer to already_AddRefed; r=Ms2ger
bug 864107 - constrain restored window dimensions to available screen area. r=ttaubert