Moves the ToName elision out of the peephole optimizer and into the
BytecodeGenerator.

BUG=v8:6194

Change-Id: Ic355adbe21f967dc5d52babdd37100a260c62c26
Reviewed-on: https://chromium-review.googlesource.com/467466
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44427}