Replace the explicit ok tracing by setting the scanner to fail, allowing us to
return automatically. RETURN_IF_PARSE_ERROR is now used instead of CHECK_OK to
verify if the parser failed.

In a follow-up CL we'll merge RETURN_IF_PARSE_ERROR after Expect* into an
EXPECT* macro. We'll keep (for now) RETURN_IF_PARSE_ERROR that guard uses of
possible NullExpression (e.g., impl()->IsIdentifier(...)). All other RETURN_IF*
will be removed. Uses after failure can likely later be fixed too by introducing
a FailureExpression.

Bug: v8:8363 ,v8:7926

Change-Id: I9896449eb9be476c453da4417a0bfd17c169ff38
Reviewed-on: https://chromium-review.googlesource.com/c/1294649
Commit-Queue: Florian Sattler <sattlerf@google.com>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56972}