Cannot scroll through previous chat messages [GAMEPLAY]

When in game, after having typed something, you can no longer press the up arrow key to revisit a message you have previously typed (particularly useful in timing cooldowns).

To replicate:

1. Type message in in-game chat (e.g. Hello!)
2. Press enter to send the message
3. Go into the chat again and press the up arrow key

What should happen: You should see the previous message (in this case, "Hello!") in the area where you can type. What happens now: The space is blank. The up key appears not to work.

For me, this has a 100% reproduction rate. I am using OSX Yosemite.