Materialized literal removal is a follow up to https://chromium-review.googlesource.com/443246

In addtion, remove ParserBase::Checkpoint; it was for restoring materialized
literal counts and expected property counts, but actually the expected property
count tracking was incorrect ("this" in arrow function param list binds to the
outside, so it's correct without the checkpoint):

(a, b = this.c = 0) => { }

BUG=

Change-Id: Ic097f6d2e7cb235166fb3a76af3bf5584bc167f0
Reviewed-on: https://chromium-review.googlesource.com/449733Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43579}