- Implement js-api changes for WebAssembly.Memory to accept a shared parameter
 - Update allocation to use SharedArrayBuffers

BUG=v8:6532

R=binji@chromium.org, bradnelson@chromium.org

Change-Id: I021491217568751b06fbd7b4b08b1dd88910e21d
Reviewed-on: https://chromium-review.googlesource.com/564058
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Reviewed-by: Brad Nelson <bradnelson@chromium.org>
Reviewed-by: Ben Smith <binji@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46543}