perf regression. See crbug.com/695653 for more info.

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.

BUG=695653
TBR=hablich@chromium.org

Review-Url: https://codereview.chromium.org/2715223003
Cr-Commit-Position: refs/heads/master@{#43462}