1 files changed, 17 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/browsers/the-window-object/support/sizing-target.html b/testing/web-platform/tests/html/browsers/the-window-object/support/sizing-target.html
new file mode 100644
index 0000000000..7cd5348a85
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/the-window-object/support/sizing-target.html
@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<script>
+  const windowProps = ["innerWidth", "innerHeight"];
+  const windowPropsObj = {};
+  const channelName = location.search.substr(1);
+  const channel = new BroadcastChannel(channelName);
+  for (const prop of windowProps) {
+    windowPropsObj[prop] = window[prop];
+  }
+  channel.postMessage(windowPropsObj);
+
+  // Because messages are not delivered synchronously and because closing a
+  // browsing context prompts the eventual clearing of all task sources, this
+  // document should not be closed until the opener document has confirmed
+  // receipt.
+  channel.onmessage = () => { window.close() };
+</script>