Change description:
Adds a new JavaScript type SharedArrayBuffer. SharedArrayBuffers can be sent to Workers and without neutering the sent buffer. The underlying buffer will be shared between the workers. The Atomic API provides atomic loads and stores and Read/Modify/Write accesses to SharedArrayBuffers. The Futex API provides the ability for a worker to wait for another worker to signal it, without having to spin-loop.

Changes to API surface:
Adds SharedArrayBuffer constructor
Adds top-level Atomics object
Modifies postMessage to allow passing SharedArrayBuffer and SharedArrayBuffer-backed typed arrays

Links:
Public standards discussion: https://github.com/tc39/ecmascript_sharedmem

Support in other browsers:
Edge: Experimental, behind a flag: https://github.com/Microsoft/ChakraCore/wiki/Release-Notes#v140
Firefox: In Firefox nightly: https://bugzilla.mozilla.org/show_bug.cgi?id=1312446
Safari: Tech Preview 20: https://developer.apple.com/safari/technology-preview/release-notes/