1 files changed, 54 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/browsers/browsing-the-web/back-forward-cache/resources/event-recorder.js b/testing/web-platform/tests/html/browsers/browsing-the-web/back-forward-cache/resources/event-recorder.js
new file mode 100644
index 0000000000..469286a399
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/browsing-the-web/back-forward-cache/resources/event-recorder.js
@@ -0,0 +1,54 @@
+// Recording events
+
+const params = new URLSearchParams(window.location.search);
+const uuid = params.get('uuid');
+
+// The recorded events are stored in localStorage rather than global variables
+// to catch events fired just before navigating out.
+function getPushedItems(key) {
+  return JSON.parse(localStorage.getItem(key) || '[]');
+}
+
+function pushItem(key, value) {
+  const array = getPushedItems(key);
+  array.push(value);
+  localStorage.setItem(key, JSON.stringify(array));
+}
+
+window.recordEvent = function(eventName) {
+  pushItem(uuid + '.observedEvents', eventName);
+}
+
+window.getRecordedEvents = function() {
+  return getPushedItems(uuid + '.observedEvents');
+}
+
+// Records events fired on `window` and `document`, with names listed in
+// `eventNames`.
+function startRecordingEvents(eventNames) {
+  for (const eventName of eventNames) {
+    window.addEventListener(eventName, event => {
+      let result = eventName;
+      if (event.persisted) {
+        result += '.persisted';
+      }
+      if (eventName === 'visibilitychange') {
+        result += '.' + document.visibilityState;
+      }
+      recordEvent('window.' + result);
+    });
+    document.addEventListener(eventName, () => {
+      let result = eventName;
+      if (eventName === 'visibilitychange') {
+        result += '.' + document.visibilityState;
+      }
+      recordEvent('document.' + result);
+    });
+  }
+}
+
+// When a comma-separated list of event names are given as the `events`
+// parameter in the URL, start record the events of the given names.
+if (params.get('events')) {
+  startRecordingEvents(params.get('events').split(','));
+}