Original issue's description:
> Use background tasks for the compiler dispatcher
>
> BUG=v8:5215
> R=marja@chromium.org,vogelheim@chromium.org
>
> Review-Url: https://codereview.chromium.org/2606263002
> Cr-Commit-Position: refs/heads/master@{#42035}
> Committed: https://chromium.googlesource.com/v8/v8/+/7a1b3a7bebbef88e72c9f7747e1930f10ee10c80

BUG=v8:5215
TBR=marja@chromium.org,vogelheim@chromium.org,rmcilroy@chromium.org

Review-Url: https://codereview.chromium.org/2613483002
Cr-Commit-Position: refs/heads/master@{#42040}