1441173 - window.promiseDocumentFlushed should not work with subframes

Status: NEW

(Core :: General, enhancement)

Description

[Mike Conley (:mconley) (:⚙️)]

window.promiseDocumentFlushed is meant to be called on top-level inner windows, and not on the outerWindows of subframes. This is also because we have this case to deal with:

   <iframe style="display: none"></iframe>
   <script>
     var i = document.querySelector("iframe");
     i.style.display = "";
     i.contentWindow.promiseDocumentFlushed(() => 1);
   </script>

With the code as it currently stands, we throw an exception here because the PresShell for the subframe doesn't exist.

The other complication is that sometimes a subframe will report that _it_ doesn't need a style or layout flush, even though its parent _does_, meaning that a style or layout flush could still occur when querying for style / layout information even though the nsGlobalWindowInner determines that no style or layout flushes are required[1]

[1]: See bug 1434376 comment 69 and bug 1434376 comment 70