gecko-dev/dom/serviceworkers/test/claim_worker_1.js

onactivate = function(e) {
  var result = {
    resolve_value: false,
    match_count_before: -1,
    match_count_after: -1,
    message: "claim_worker_1"
  };

  self.clients.matchAll().then(function(matched) {
    // should be 0
    result.match_count_before = matched.length;
  }).then(function() {
    return self.clients.claim();
  }).then(function(ret) {
    result.resolve_value = ret;
    return self.clients.matchAll();
  }).then(function(matched) {
    // should be 2
    result.match_count_after = matched.length;
    for (i = 0; i < matched.length; i++) {
      matched[i].postMessage(result);
    }
    if (result.match_count_after !== 2) {
      dump("ERROR: claim_worker_1 failed to capture clients.\n");
    }
  });
}