Steps to reproduce:
1. Open Unity
2. Create a UI element with a RectTransform and make it into a prefab
3. Press "Apply" on that prefab instance
4. Values are marked bold, as if a change was made, but they're not saved yet.
5. Check the prefab in the project view - changes were saved
6. Press "Revert" on prefab instance
7. Nothing happens

Expected: Applying and Reverting prefab instance works properly by either applying changes or discarding them
Actual: Applying changes actually saves them to the prefab, but shows them as unsaved while Revert does nothing at all

Reproduced on: 5.5.4p1, 5.6.2p2, 2017.1.0f3, 2017.2.0b2