message: Rejects when Chrome storage object is not available.
diff: @@ -253,6 +253,7 @@ function SyncService($q) {
  }
  return $q((resolve, reject) => {
  + if (chrome.storage && chrome.storage.sync) {
  chrome.storage.sync.remove(key, () => {
  if (chrome.runtime.lastError) {
  reject(chrome.runtime.lastError);
  @@ -260,6 +261,9 @@ function SyncService($q) {
  resolve();
  }
  });
  + } else {
  + reject('Chrome storage object is not available.');
  + }
  });
  }
  