[FlatButton] Add className property

[Shahrukh-Zindani]

Adds className to FlatButton property. Close issue #5906.

[oliviertassinari]

Documenting the className on the master is a good idea. That's an exception to the "we don't document native properties" as it's an important customization one.

[oliviertassinari]

Actually, I'm wondering, do we need to explicit the className property here? If you don't destructure it, it will be inside the other object. That would reduce the number of ligne of code.

[oliviertassinari]

(better for perf)

[Shahrukh-Zindani]

@oliviertassinari I tried removing this line from here and className does not work. Looks like it is not inside the other object.

[oliviertassinari]

If you destructure it, it won't be inside. That's expected.

[Shahrukh-Zindani]

I am not able to understand your approach to handle className. className is not defined in EnhancedButton or its parent so according to my understanding we would have to explicitly need a className property here to make it work. Can you confirm my understanding or give an example to show me how you would make it work without explicitly having className property there.

[oliviertassinari]

Just keep the className propTypes. That should do the work.

[Shahrukh-Zindani]

Got it. This is ready to get merged now.