Show a disabled geolocate button if user or system denies geolocation

[kkaefer]

Fixes #8870

This PR adds a new icon to be shown when the user or the system denied permission to use the location. It's shown when geolocation is disabled outright in Firefox and Chrome, or when the user or the system explicitly denies location after being prompted.

There are a few caveats:

• It's not possible to detect whether the user has denied location to begin with when loading a page. Safari doesn't implement navigator.permissions detection. Once the user has click on the geolocate button, the state is set correctly though.
• When macOS location services are disabled on a system-wide level, Firefox never calls any of the callbacks, and the location indicator keeps spinning. This is a bug in Firefox and tracked in https://bugzilla.mozilla.org/show_bug.cgi?id=1529591
• When macOS location services are disabled, Chrome sneakily circumvents the OS setting and generates a location from different sources (e.g. IP address or Wifi networks; in my case, the location was approximate, but still in the same neighborhood).

Before this patch, the geolocate button was hidden when geolocation was disabled. It is now being shown, but in the new disabled state.

I'm a bit unsure how to test this correctly, since it depends on complex interaction between the OS, and the user clicking on various browser UIs.

/cc @andrewharvey

[ryanhamley]

This looks good to me. How did you test on Safari? I just get an error that geolocation is disabled over http.

[ryanhamley]

I'm a bit unsure how to test this correctly, since it depends on complex interaction between the OS, and the user clicking on various browser UIs.

Another argument for adding an end-to-end test suite

[andrewharvey]

Could we update the title/aria-label when disabled to be something like "Location not available"?

[andrewharvey]

This is good!

We should make sure to include a note in the changelog since the behaviour has changed. Anyone who prefers to hide the control when not available can still override the css .mapboxgl-ctrl-geolocate:disabled { display: none }.

[andrewharvey]

Could we update the title/aria-label when disabled to be something like "Location not available"?

[kkaefer]

I tested in Safari in the following way:

brew install mkcert
mkcert -install
mkcert localhost

python -c "import BaseHTTPServer, SimpleHTTPServer, ssl; \
           handler = SimpleHTTPServer.SimpleHTTPRequestHandler; \
           httpd = BaseHTTPServer.HTTPServer(('localhost', 4443), handler); \
           httpd.socket = ssl.wrap_socket(httpd.socket, \
                                          certfile='./localhost.pem', \
                                          keyfile='./localhost-key.pem', \
                                          server_side=True); \
           httpd.serve_forever()"

Then accessed the server at https://localhost:4443/debug/debug.html

[kkaefer]

Added the title and aria-label, and addressed all review feedback.

addressed review comments