This abstract class (and AngularJSUrlCodec) are used for serializing and deserializing pieces of a URL string. AngularJS had a different way of doing this than Angular, and using this class in conjunction with the LocationUpgradeService an application can have control over how AngularJS URLs are serialized and deserialized.
PR Close#30055
AngularJS's `$location` service doesn't have a direct counterpart in Angular. This is largely because the `Location` service in Angular was pulled out of the `Router`, but was not purpose-built to stand on its own.
This commit adds a new `@angular/common/upgrade` package with the beginnings of a new `LocationUpgradeService`. This service will more closely match the API of AngularJS and provide a way to replace the `$location` service from AngularJS.
PR Close#30055
Jason Aden