* which may be {@code element} itself.
   */
  @CanIgnoreReturnValue
  @Override
  public boolean offer(E element) {
    checkNotNull(element);
    modCount++;
    int insertIndex = size++;

    growIfNeeded();

    // Adds the element to the end of the heap and bubbles it up to the correct
    // position.
    heapForIndex(insertIndex).bubbleUp(insertIndex, element);