This merges all the possible targets for 'member expressions' previously
parsed in ParseMemberExpression into ParsePrimaryExpression; since that's
not independently used anyway. This will make it faster since we don't
need to go through unnecessary branches before ParsePrimaryExpression on
the fast path, *and* it will make the binary smaller since
ParseMemberExpression is inlined but ParsePrimaryExpression is not. It
saves 4kb. Yay :)

Bug: chromium:913222
Change-Id: Ib92e1c2a128fffff1db85b625bb5f311ec8c24ef
Reviewed-on: https://chromium-review.googlesource.com/c/1480379
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59814}