Views Proximity Filter allow client location as default

Problem/Motivation

Views Proximity Filter is a great way to allow users to do a proximity search. It would be cool, if the input field could, instead of static values, default to the user's location. That way the view could initially show proximity values but would still be searchable / changable for users.

Steps to reproduce

Proposed resolution

Add an option for the "Geocode Origin" source to use the Client Location as default value (if the user allowed it). What do you think?

Remaining tasks

User interface changes

API changes

Data model changes