Previously, we had lazy parsing of class constructor disabled when a
class literal had class fields because we were using a reference to
the initializer function variable to load the function and call it.

Instead, in this patch, we use the scope analysis to lookup this
initializer function variable.

Bug: v8:5367
Change-Id: Ib73d7e6abed33c04d1f574e7976bea4869d54757
Reviewed-on: https://chromium-review.googlesource.com/768384
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49406}