In https://chromium-review.googlesource.com/c/472247/, I avoided
running DesugarLexicalBindingsInForStatement() if there were no lexical
loop variables, the function was not resumable, and the variables are
not captured by eval or a function declaration.

I think it's now possible to limit this further, and only do the more
extensive desugaring if there's a function declaration / eval() call
in the loop body. `yield` and `await` are not an issue as those loop
variables are written to the register file and not lost.

This change just removes the `is_resumable()` condition. If it passes
tests, I think it's safe.

BUG=v8:4762, v8:5460, v8:6579

Change-Id: I92d0308ad9401c1338411bc9ae9021f978803d3a
Reviewed-on: https://chromium-review.googlesource.com/563587
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46536}