This reverts the previous revert, commit
5a04f4fd.

Previously reverted changes:

>    Revert "[SAB] Move Atomics builtins to C++"
>
>     This reverts commit 2b9840d8.
>
>     Revert "[SAB] Remove unreachable Uint8Clamped atomics paths"
>
>     This reverts commit d1160fb1.
>
>     Revert "Remove tiny unit test for MinSimple/MaxSimple"
>
>     This reverts commit 837760ec.
>
>     Revert "Remove infrastructure for experimental JS natives"
>
>     This reverts commit 8cfe45b6.

These changes were reverted to improve a perf regression on a Chrome
bot. Since then, the regression has reappeared, then disappeared again
all from seemingly unrelated changes.

BUG=v8:6033
TBR=adamk@chromium.org,hpayer@chromium.org,yangguo@chromium.org

Review-Url: https://codereview.chromium.org/2732213005
Cr-Commit-Position: refs/heads/master@{#43758}