LibWeb: Convert Layout Boxes to new pixel units

Author: https://github.com/AtkinsSJ
Commit: 65cdf89a8b
Pull-request: https://github.com/SerenityOS/serenity/pull/16514
Reviewed-by: https://github.com/MacDue
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/Layout/ImageBox.h

@@ -45,7 +45,7 @@ private:
 
     ImageLoader const& m_image_loader;
 
-    Optional<float> m_cached_alt_text_width;
+    Optional<CSSPixels> m_cached_alt_text_width;
 };
 
 }