script: Manage <iframe> sizes in Window (#34643)

Manage `<iframe>` size updates in `Window`. In addition to removing
duplicated code, this will allow setting `<iframe>` sizes synchronously
on child `Pipeline`s of the same origin in the script process in a
followup change. The goal is remove flakiness from `<iframe>` sizing.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/dom/htmliframeelement.rs

@@ -196,7 +196,7 @@ impl HTMLIFrameElement {
 
         let window_size = WindowSizeData {
             initial_viewport: window
-                .inner_window_dimensions_query(browsing_context_id, can_gc)
+                .get_iframe_size_if_known(browsing_context_id, can_gc)
                 .unwrap_or_default(),
             device_pixel_ratio: window.device_pixel_ratio(),
         };