Does not remove the extra private state added, as doing so seems to break the
debugger.

Fixes new Test262 tests:
- built-ins/Promise/race/same-resolve-function
- built-ins/Promise/race/same-reject-function

BUG=v8:4632
LOG=N
R=littledan@chromium.org, cbruni@chromium.org

Review URL: https://codereview.chromium.org/1538853002

Cr-Commit-Position: refs/heads/master@{#33214}