This reverts commit acf09252.

Reason for revert: Undesired side effects.

Original change's description:
> [turbofan] Force creation of initial maps upfront.
> 
> When encountering a JSFunction, generate its initial map (if
> appropriate).  This ensures that we can depend on the initial
> map during optimization.
> 
> We are not sure about the performance impact of this change, it
> might cause regressions.
> 
> R=​jarin@chromium.org, mslekova@chromium.org
> 
> Bug: v8:7790, chromium:875175
> Change-Id: I4bbf62e30730f55a53d9bb7eee62c87d820616fb
> Reviewed-on: https://chromium-review.googlesource.com/1180970
> Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
> Reviewed-by: Maya Lekova <mslekova@chromium.org>
> Commit-Queue: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#55253}

TBR=jarin@chromium.org,neis@chromium.org,mslekova@chromium.org

Change-Id: I322f504d068f752b218680f633b8719864ca4950
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7790, chromium:875175
Reviewed-on: https://chromium-review.googlesource.com/1183341Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55266}