To reproduce the bug, open the URL, copy some text to the clipboard, focus the text field and press Command-V. Instead of the text being pasted into the field, the caret disappears. Blurring and refocusing the field doesn't bring the caret back. This is not reproducible with just any text field (e.g. the google.com text field).
For example, the bug doesn't happen with <div><input></div>.
Regressed in <http://trac.webkit.org/projects/webkit/changeset/21093>.
I ran into this too! It's been preventing me from working on some bugs!
<rdar://problem/5168938>
Created attachment 14247 [details] Test case This shows the root cause of the bug (which is not in editing or in form controls). The inner (green) div's layer gets lost due to the "!fullRemove/Insert/Append" shortcuts introduced in r21093.
Created attachment 14248 [details] Avoid cutting off layers when removing an anonymous block
Comment on attachment 14248 [details] Avoid cutting off layers when removing an anonymous block r=me
Sending LayoutTests/ChangeLog Adding LayoutTests/fast/dynamic/anonymous-block-layer-lost-expected.checksum Adding (bin) LayoutTests/fast/dynamic/anonymous-block-layer-lost-expected.png Adding LayoutTests/fast/dynamic/anonymous-block-layer-lost-expected.txt Adding LayoutTests/fast/dynamic/anonymous-block-layer-lost.html Sending WebCore/ChangeLog Sending WebCore/rendering/RenderBlock.cpp Transmitting file data ....... Committed revision 21173.