Backed out changeset 09cca9f32103 (bug 848731) for mochitest-bc failures.
Bug 916322 - Add UnsetAttr to HTMLCanvasElement to catch the removal of attributes and keep the context it owns of matching size. r=khuey, r=jmuizelaar

The test is debug only, asserting without this fix.
Bug 907077: Change for-of to conform to latest ES6 specification. r=jwalden

--HG--
extra : rebase_source : 93c5b9d6a28a42468d9ca9ac7da3b4e1b6d92820
Bug 917991 - Cleanup the mechanism by which movapd and movaps are used for register-to-register moves. r=jandem