Post-commit review follow-up:
This works better for properties that were all-caps, such as `URL`.
Thanks @harlanhaskins for the tip!
rdar://problem/32845968
We used to only migrate them in call sites, e.g. changing from
``p.getHeight()`` to ``p.Height``. However, with experimenting on more real-world
projects, we realize migrating overrides is equally important.
rdar://32265583
Based on recommendations in SE-0160, there are two migration workflows:
- Conservative: Maintain @objc visibility that was inferred in Swift 3
by adding @objc to all declarations that were implicitily visible to
the Objective-C runtime. This is invoked in the migrator by adding the
-migrate-keep-objc-visibility flag.
- Minimal: Only declarations that must be visible to Objective-C based
on their uses (or in cases like dynamic vars) are migrated.
rdar://problem/31876357
