Bug 852802 - Add incremental needsBarrier to the runtime and check it first; r=billm

--HG--
rename : content/svg/content/src/SVGFETurbulenceElement.h => content/svg/content/src/nsSVGFilters.cpp
extra : rebase_source : d30970922e139e6d1a87bbdf53f27b4e67313b08