The window is transparent before the first Web content is painted

[felipeerias]

Configuration

This happens on devices where we support XR layers, like Meta and PICO.

Steps to Reproduce

1. Launch Wolvic or open a new window

Current Behavior

The window is fully transparent before the first Web content is painted, so it appears invisible to the user.

Expected Behavior

The window shows an opaque background (e.g. white) while the Web content is prepared.

[svillar]

We had similar issues in the past, check previous solutions