Research: Rendering to buffer when content contains autoresizable images.

[raveclassic]

We need to support a case when scrollable content contains autoadjustable images that lead to race condition when scrollbar appears and then hides.

1. When content height is greater than available height scrollbar appears - expected behavior.
2. When scrollbar appears available content width is reduced by the width of scrollbar.
3. When content width is reduced attached image width is also reduced.
4. Because image width is reduced and image proprotions are preserved image height is also reduced.
5. When image height and width are reduced, content height is reduced and then it fits into available height - so scrollbar should be hidden.
6. Hiding scrollbar increases available width which leads to increasing image height and so on - race condition.

Native chrome behavior is to check new height in background with added scrollbar and compare with current. We need to research same mechanism of height checking.