This reverts commit a9428d52.

Original change's description:
 > [heap, runtime] Fix data race in prototype map transition during
 > concurrent marking.
 >
 > BUG=chromium:694255
 >
 > Change-Id: I172167623e9deab692fb506d7d4211d210b09a80
 > Reviewed-on: https://chromium-review.googlesource.com/579092
 > Reviewed-by: Igor Sheludko <ishell@chromium.org>
 > Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
 > Cr-Commit-Position: refs/heads/master@{#46813}

Change-Id: Ib4b4b989620800ce8a4f4247e4dae2a88c186be9
Reviewed-on: https://chromium-review.googlesource.com/581194Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46819}