This reverts commit 68212c80.

Reason for revert: https://build.chromium.org/p/client.v8/builders/V8%20Linux%20-%20noi18n%20-%20debug/builds/17200

Original change's description:
> RegExp: Add the ability to switch flags on and off within the regexp
> 
> R=​yangguo@chromium.org
> 
> This is a reupload of https://chromium-review.googlesource.com/c/v8/v8/+/571746
> with a different user, since the other one was not allowed to commit to V8 any
> more.
> 
> Bug: 
> Change-Id: I6171afd44e514f6c934390faab6f9bee3953ac77
> Reviewed-on: https://chromium-review.googlesource.com/752522
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49098}

TBR=erik.corry@gmail.com,yangguo@chromium.org,erikcorry@chromium.org,jgruber@chromium.org

Change-Id: I651c5618f09f43104af50cb1319ab7b49011573e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/752802Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49099}