Key type checking nodes cause the BP to become dirty upon reopening it

All "Key" related BlueprintPure nodes cause the Blueprint to become dirty when the Blueprint is reopened.

This includes:
Key Get Display Name
Key Is Float Axis
Key Is Gamepad Key
Key Is Keyboard Key
Key Is Modifier Key
Key Is Mouse Button
Key Is Vector Axis

Per James B.:
Just having any of these nodes in the event graph (not even hooked up) causes the blueprint to be flagged as "Dirty; needs to be recompiled." Tracking this issue down to the code shows that these nodes all call the function "FKey::ConditionalLookupKeyDetails()," which modifies a member property. This issue occurs in the UE4-Fortnite branch.

1. Open any Blueprint's event graph.
2. Place a "Key Is Gamepad Key" node.
3. Compile and Save the Blueprint.
4. Close the Blueprint.
5. Open the Blueprint.

Result:
Blueprint is dirty once it's opened.