Revert of Disable the CompilerDispatcher if we don't have idle time (patchset #1 id:1 of https://codereview.chromium.org/2600743002/ )

Reason for revert:
[Sheriff] Speculative revert since we got persistent timeouts on win32 debug:
https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20debug/builds/6417

Please reland if it doesn't help.

Original issue's description:
> Disable the CompilerDispatcher if we don't have idle time
>
> Since we can't do all steps on background threads, we need idle time to
> work
>
> BUG=v8:5215
> R=danno@chromium.org
>
> Review-Url: https://codereview.chromium.org/2600743002
> Cr-Commit-Position: refs/heads/master@{#41944}
> Committed: https://chromium.googlesource.com/v8/v8/+/a0d9eb346bba90aa0b32a2d3184cbbfd6adb243e

TBR=danno@chromium.org,jochen@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5215

Review-Url: https://codereview.chromium.org/2600773002
Cr-Commit-Position: refs/heads/master@{#41948}