This reverts commit 72b88fda.

Reason for revert: Changes a layout test:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/16595

Original change's description:
> [runtime] Make all built-in functions strict.
> 
> According to ES#sec-built-in-function-objects all built-in functions
> must be strict.
> 
> This is a preliminary CL before changing the way we define built-in
> functions in native JS files.
> 
> Bug: v8:6459
> Change-Id: I8e60b342f04ea1b0843fe1990334cbb9b26ebac4
> Reviewed-on: https://chromium-review.googlesource.com/546215
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Adam Klein <adamk@chromium.org>
> Commit-Queue: Igor Sheludko <ishell@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#46237}

TBR=adamk@chromium.org,ishell@chromium.org,verwaest@chromium.org

Change-Id: Ic458b478b2dd23aae7ea2a51aa6052c1f5931c56
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6459
Reviewed-on: https://chromium-review.googlesource.com/549322Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46242}