If animation has less than two keyframes, events will not be triggered. Using one keyframe also does not work.

To reproduce:
1. Open attached project "New Unity Project 1.zip"
2. Open "events.unity" scene
3. Select "Cube Event" game object from the hierarchy
4. Open Animation window and observe as there is one event placed on 0.0 timeline
5. Enter play mode and observe the console as there are no logs
6. Exit play mode
7. Disable "Cube Event" game object and enable "Cube Keyframes"
8. Observe in the Animation window as it has the same event but with two keyframes
9. Enter play mode
10. Observe in the console as log are being registered

Expected result: events are triggered even without keyframes
Actual result: events are not triggered when having less than two keyframes

Reproduced on: 5.6.1f1 2017.1.0b10 2017.2.0a4
Not reproduced on: 5.5.4f1
Regression introduced on: 5.6.0b3

Also reproduced on: 5.6.0b4
Also not reproduced on: 5.6.0a1 5.6.0b1 5.6.0b2