public @NotNull Collection<@NotNull String> getManualWatchRoots() {
    Set<String> result = null;
    for (Set<String> rootSet : myManualWatchRoots.values()) {
      //noinspection SynchronizationOnLocalVariableOrMethodParameter
      synchronized (rootSet) {
        if (result == null) {
          result = new HashSet<>(rootSet);
        }
        else {
          result.retainAll(rootSet);
        }
      }
    }
    return result != null ? result : Collections.emptyList();
  }
public @NotNull Collection<@NotNull String> getManualWatchRoots()