firebase-ios-sdk

Fix a couple of race conditions and module import of a private header (#5187)

* Fix a couple of race conditions and module import of a private header

The header and API in question should be considered hidden. An alternative would be expose the API in the private header .

A race condition existed in the upload package itself--it should hand copies of itself and not self to prevent asynchronous mutation whilst a different queue is also executing an asynchronous mutation. One alternative would be to create mutable an immutable variants of the package. This could manifest as an EXC_BAD_ACCESS in GDTCCTPrioritizer.m

* Assert that the IMP is present, because there shouldn't be a silent failure