They've been replaced by using constructor nodes, so any code handling conversion operators
can be removed.

BUG=380353

Change-Id: I70413179e7443efccbf997a5dd0f053c23689589
Reviewed-on: https://chromium-review.googlesource.com/203453Tested-by: Nicolas Capens <nicolascapens@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>