Revert of Add script context with context-allocated "const this" (patchset #2 id:20001 of https://codereview.chromium.org/1173333004/)

Reason for revert:
nosnap failure

Original issue's description:
> Add script context with context-allocated "const this"
>
> This is a reapplication of https://codereview.chromium.org/1179893002/.
>
> R=rossberg@chromium.org,mstarzinger@chromium.org
> LOG=N
> BUG=498811
>
> Committed: https://crrev.com/cfc764f4050edc74aef92daa4c39ccc113893968
> Cr-Commit-Position: refs/heads/master@{#28994}

TBR=mstarzinger@chromium.org,rossberg@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=498811

Review URL: https://codereview.chromium.org/1177903004

Cr-Commit-Position: refs/heads/master@{#28996}