Auto merge of #21051 - jonathanKingston:window-length, r=jdm

Implement window.length DOM attribute.

Implements the `window.length` DOM attribute for enumerating frames on the document.

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2 files changed, 7 insertions, 1 deletions

diff --git a/components/script/dom/webidls/Window.webidl b/components/script/dom/webidls/Window.webidl
index 0cda7d2d800..8416cd49334 100644
--- a/components/script/dom/webidls/Window.webidl
+++ b/components/script/dom/webidls/Window.webidl
@@ -31,7 +31,7 @@
 
   // other browsing contexts
   [Replaceable] readonly attribute WindowProxy frames;
-  //[Replaceable] readonly attribute unsigned long length;
+  [Replaceable] readonly attribute unsigned long length;
   // Note that this can return null in the case that the browsing context has been discarded.
   // https://github.com/whatwg/html/issues/2115
   [Unforgeable] readonly attribute WindowProxy? top;
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 756bfb5a555..2db7609bec4 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -694,6 +694,12 @@ impl WindowMethods for Window {
         self.window_proxy()
     }
 
+    // https://html.spec.whatwg.org/multipage/#accessing-other-browsing-contexts
+    fn Length(&self) -> u32 {
+        let doc = self.Document();
+        doc.iter_iframes().count() as u32
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-parent
     fn GetParent(&self) -> Option<DomRoot<WindowProxy>> {
         // Steps 1-3.