Bug 948128. Add StackArray helper. r=Bas

This is helpful for when we want to convert between
different types and we need a short lived piece of memory.

--HG--
extra : rebase_source : b841a535cb1ddd837df4b34949bd34054c438c67
Bug 785905 - Build Ion MIR graph off thread, r=jandem.
Bug 950716 - SpiderMonkey: A minor BitSet::Iterator refactoring. r=nbp
Bug 950716 - IonMonkey: Optimize BitSet a little r=nbp
Bug 950716 - IonMonkey: Reorder struct fields for micro-efficiency. r=nbp
Bug 949108 - Fix an exact rooting false positive across the activity callback; r=bholley

--HG--
extra : rebase_source : 9c4f0b94b376f9a2d11c5f031b8a8ef27aa2e4fb
Merge m-c to inbound.
Bug 950456 - Fix tracing for baseline type monitor and update stubs, r=jandem.
Bug 950503 - Build accessible/src/windows in unified mode; r=tbsaunde
Bug 950293 (Part 1) - Fix handling of little-endian EXIF data. r=tn
Bug 877115 - [Moz2Dify] Part 1. Remove ImageFormat typedef from GLContext. (r=nical)
Bug 877115 - [Moz2Dify] Part 2. Moz2Dify GLContext::ResizeOffscreen signature. (carries r=nical)
Bug 877115 - [Moz2Dify] Part 3. Change gfxIntSize to gfx::IntSize in GLContext::OffscreenSize and dependendent classes. r=nical
Bug 877115 - [Moz2Dify] Part 4. Change gfxIntSize to gfx::IntSize in GLScreenBuffer and friends. (carries r=nical)
Bug 877115 - [Moz2Dify] Part 5. Minimize gfxIntSize usage in GLContext. r=nical
Bug 877115 - [Moz2Dify] Part 6. Moz2Dify  SharedSurface_EGLImage::GetPixels. r=nical
Bug 950281 - micro-optimize NS_TableDrivenQI by ensuring the table has at least 1 non-null entry; r=bsmedberg
Bug 950527 - Mark asm.js success messages as not being an error (r=bbouvier)
Bug 937089 - Deoptimize arguments when it is redeclared as a variable inside a with statement inside an eval, r=luke.
Bug 950658 - Clear pending exception in HeapTypeSetKey::instantiate on OOM. r=bhackett

--HG--
extra : rebase_source : 8f8c28f51ee7f08ef822fec5ac590a7d1cfebed7