tree cb5be837f0cfc87122e76219d0def8780b2f0ed6
parent e18aa2eda7835007c805c07cb3c4025aebda7b94
author Thomas Van Lenten <thomasvl@google.com> 1663267215 -0400
committer Thomas Van Lenten <thomasvl@google.com> 1663601913 -0400

Provide a protocol for GPBExtensionRegistry's lookup support.

This allows some to use an alternative registry if they have a different
implementation.

This is really just wiring though the change to use the GPBExtensionRegistry
protocol vs the concrete GPBExtensionRegistry through the other apis.