Show horizontal scrollbar and auto height based on iframe content

Show horizontal scrollbar and auto height based on iframe content.

This pull request still have two problems.

1. It auto increase height when iframe content height is dynamically increased.
    but it does not reduce height when iframe content height is dynamically reduced.

2. Horizontal scrollbar is displayed only if it is necessary.
    in this case, horizontal scrollbar adds small height and iframe also creates vertical scrollbar.