refactor(service-worker): make the caching behavior more explicit (#30977)

This commit doesn't change the behavior wrt caching, but it makes it
more explicit that only non-timed-out responses are cached. In case of a
timeout, `res` would be set to a programmatically created 504
`Response`, so `cacheResponse()` (which checks for `res.ok`) would not
have cached it anyway, but this makes change makes it more explicit (and
more similar to the equivalent part in [handleFetchWithFreshness()][1]).

[1]: https://github.com/angular/angular/blob/2b4d5c754/packages/service-worker/worker/src/data.ts#L379-L388

PR Close #30977

packages/service-worker/worker/src/data.ts

@@ -354,10 +354,11 @@ export class DataGroup {
 
       // Cache the network response eventually.
       ctx.waitUntil(this.safeCacheResponse(req, networkFetch));
+    } else {
+      // The request completed in time, so cache it inline with the response flow.
+      await this.cacheResponse(req, res, lru);
     }
 
-    // The request completed in time, so cache it inline with the response flow.
-    await this.cacheResponse(req, res, lru);
     return res;
   }