If you reduce the size of a long (tall) post and then Cancel, Preview, or Reply, then you can end up with neither the post nor the text area on-screen.

One way to reproduce:

• Reply to some topic high up on an active page.
• enter [[File:Cucurbita moschata Butternut 2012 G2.jpg|400x]] (deliberate typo)
• click [Preview]

You see preview of the enormous image.

• So scroll down to the reply textarea and fix the 400x to 400px
• click [Preview] or [Reply]

(Flow may one day auto-thumbnail large images; in that happens you can reduce a long post with lots of paragraphs to a line of text.)
Because the preview is so much smaller, you are left staring at some random part of the board below the original tall post, with neither the image nor textarea visible.

Also happens when you edit an existing post and reduce its size way down, or when you Cancel a tall post.

Expected results:
All these actions should scroll the new post or its preview of it into view. Cancel should scroll the place where you initiated the now-cancelled post back into view.

Version: master
Severity: normal