[<geolocation> element] Fixing minor IDL misalignment.

We can rely on `[Reflect]` to correctly handle the boolean `autolocate`
and `watch` attributes, and treat `position` and `error` as explicitly
nullable.

Bug: 461543463
Change-Id: Ia8918aa2fa69649cdf95110779271c67e73f10bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7167053
Commit-Queue: Mike West <[email protected]>
Reviewed-by: Thomas Nguyen <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1546990}

Author: mikewest

interfaces/geolocation-element.tentative.idl

@@ -30,8 +30,8 @@ interface mixin InPagePermissionMixin {
 interface HTMLGeolocationElement : HTMLElement {
   [HTMLConstructor] constructor();
 
-  readonly attribute GeolocationPosition position;
-  readonly attribute GeolocationPositionError error;
+  readonly attribute GeolocationPosition? position;
+  readonly attribute GeolocationPositionError? error;
   [CEReactions, Reflect] attribute boolean autolocate;
   [CEReactions, Reflect] attribute boolean watch;