Fix SplitHugeSwitchPass
Fix SplitHugeSwitchPass

Summary:
Accept splitting virtual methods, in which case the cloned method must be virtual, too.

It would be possible to make the clone static, but there is no advantage to that at this stage.

Reviewed By: newobj

Differential Revision: D22418848

fbshipit-source-id: b15b2c7e328352d5bebf64ff4672c541f6c30be3

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