LibWeb: Use CSS Pixels for viewport rects

Author: https://github.com/AtkinsSJ
Commit: 4084c66ad2
Pull-request: https://github.com/SerenityOS/serenity/pull/16514
Reviewed-by: https://github.com/MacDue
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/CSS/StyleComputer.h

@@ -93,7 +93,7 @@ private:
     template<typename Callback>
     void for_each_stylesheet(CascadeOrigin, Callback) const;
 
-    Gfx::IntRect viewport_rect() const;
+    CSSPixelRect viewport_rect() const;
     CSSPixels root_element_font_size() const;
 
     struct MatchingRuleSet {