To reproduce:
1. Open Animator and Animation windows
2. Open scene '111'
3. Select Directional Light game object in the Hierarchy
4. Switch the Animation's window to the Curves tab.
5. Right click on any animation curve key and select Edit key...
6. Try to change numbers in editable field

Expected result: labels should be aligned to the left side as before clicking Edit key
Actual result: after editing, labels are aligned to the right. Also, if you change numbers in editable field in 5.6.0a3 and 5.6.0a5 versions, Unity will crash.

Reproduced on: 5.4.2f1, 5.4.3f1, 5.5.0b9, 5.5.0b11, 5.5.0f2, 5.5.0f3, 5.6.0a3, 5.6.0a5