Port 6768456d

Original commit message:

    The old code was using VariableMode, but that signal is both
    over-pessimistic (some CONST and LET variables need no hole-initialization)
    and inconsistent with other uses of the InitializationFlag enum (such
    as %LoadLookupSlot).

    This changes no observable behavior, but removes unnecessary hole
    initialization and hole checks in a few places, including
    block-scoped function declarations, super property lookups,
    and new.target.

R=adamk@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2229383004
Cr-Commit-Position: refs/heads/master@{#38551}