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const params = new URLSearchParams(window.location.search);
const uuid = params.get('uuid');
// Executor and BFCache detection
// When navigating out from this page, always call
// `prepareNavigation(callback)` synchronously from the script injected by
// `RemoteContext.execute_script()`, and trigger navigation on or after the
// callback is called.
// prepareNavigation() suspends task polling and avoid in-flight fetch
// requests during navigation that might evict the page from BFCache.
//
// When we navigate to the page again, task polling is resumed, either
// - (BFCache cases) when the pageshow event listener added by
// prepareNavigation() is executed, or
// - (Non-BFCache cases) when `Executor.execute()` is called again during
// non-BFCache page loading.
//
// In such scenarios, `assert_bfcached()` etc. in `helper.sub.js` can determine
// whether the page is restored from BFCache or not, by observing
// - `isPageshowFired`: whether the pageshow event listener added by the
// prepareNavigation() before navigating out, and
// - `loadCount`: whether this inline script is evaluated again.
// - `isPageshowPersisted` is used to assert that `event.persisted` is true
// when restored from BFCache.
window.isPageshowFired = false;
window.isPageshowPersisted = null;
window.loadCount = parseInt(localStorage.getItem(uuid + '.loadCount') || '0') + 1;
localStorage.setItem(uuid + '.loadCount', loadCount);
window.pageShowPromise = new Promise(resolve =>
window.addEventListener('pageshow', resolve, {once: true}));
const executor = new Executor(uuid);
window.prepareNavigation = function(callback) {
window.addEventListener(
'pageshow',
(event) => {
window.isPageshowFired = true;
window.isPageshowPersisted = event.persisted;
executor.resume();
},
{once: true});
executor.suspend(callback);
}
// Try to disable BFCache by acquiring and never releasing a Web Lock.
// This requires HTTPS.
// Note: This is a workaround depending on non-specified WebLock+BFCache
// behavior, and doesn't work on Safari. We might want to introduce a
// test-only BFCache-disabling API instead in the future.
// https://github.com/web-platform-tests/wpt/issues/16359#issuecomment-795004780
// https://crbug.com/1298336
window.disableBFCache = () => {
return new Promise(resolve => {
// Use page's UUID as a unique lock name.
navigator.locks.request(uuid, () => {
resolve();
return new Promise(() => {});
});
});
};
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