Chat textbox isn't editable upon navigating to it with the keyboard

[jpd236]

If you use the Tab key to navigate to the Chat textbox on a puzzle page (e.g. click on the chat history pane, then press tab), it doesn't accept text input and the cursor doesn't blink. But it does appear to be focused.

Hitting enter triggers the usual onKeyDown listener, which submits the contents (if not empty) and does appear to put things into the right state. Similarly, clearing the contents on focus does work around the problem, but (naturally) clears the contents if some were present. I tried calling Transforms.select(editor, Editor.end(editor, [])); in an onFocus listener, but that doesn't seem to have done the trick.

Feels like the ideal behavior is to (1) ensure that text entry works on focus, and (2) set the cursor to the end position. This matches e.g. the Gmail email compose window behavior, from what I can tell. Unfortunately, I'm not quite sure how to make it work.