Modernize window.crypto access constants

src/crypto/crypto.ts

@@ -40,6 +40,21 @@ if (!TextEncoder) {
 }
 /* eslint-enable @typescript-eslint/no-var-requires */
 
+// Service workers don't have a useful `window` instance to pull these details off of, and in at least Chrome when
+// `window.$thing` is accessed, `$thing` will be non-null but complain about being undefined when accessed further.
+// To avoid spurious errors, we just override the crypto bits explicitly.
+if (isServiceWorker(globalThis)) {
+    crypto = globalThis.crypto;
+    subtleCrypto = globalThis.crypto.subtle ?? globalThis.crypto.webkitSubtle;
+    TextEncoder = globalThis.TextEncoder;
+}
+
+// Window is a close enough approximation for what we need it for.
+function isServiceWorker(globalThis: any): globalThis is Window {
+    // Note: `skipWaiting` is a function exclusive to service workers.
+    return typeof globalThis["skipWaiting"] === "function";
+}
+
 export function setCrypto(_crypto: Crypto): void {
     crypto = _crypto;
     subtleCrypto = _crypto.subtle ?? _crypto.webkitSubtle;