Copy and paste doesn't work in 1.2.5

Verification builds: 1.2.5 (530691)

Summary: Previously, it was possible to Ctrl + A to select text (or shift + left), Ctrl + C and Ctrl + V in the chat or on a command block. It was pretty handy, especially for coordinates.

Impact: Copy and paste no longer works.

Repro Steps:

1. Type something in the chat (don't send)
2. Press Ctrl + A to highlight (will not visually highlight, but normally does actually select)
3. Press Ctrl + C (copy)
4. Press Ctrl + V (paste)
5. No longer works

Observed Results: Previous builds (for quite some time) have supported copy and paste.

Expected Results: Should copy and paste.

Screenshots/Videos attached: No

Notes: