@interface FIRStorageTask : NSObject
A superclass to all FIRStorage*Tasks, including FIRStorageUploadTask and FIRStorageDownloadTask, to provide state transitions, event raising, and common storage or metadata and errors. Callbacks are always fired on the developer specified callback queue. If no queue is specified by the developer, it defaults to the main queue. Currently not thread safe, so only call methods on the main thread.