* FIRStorageUploadTask: validate data and fileURL before upload (#2350)
* FIRStorageReferenceTests: Verify a specific error (#2350)
* Code cleanup. More informative error.
* FIRStorageReference: error message, test fix (#2350)
* Run ./scripts/style.sh
* #2350: Punctuation
* FIRStorageReferenceTests: naming (#2350)
* Run ./scripts/style.sh
* Tests fixed (#2350)
* FIRStorageReferenceTests fixed for Mac OS (#2350)
* FIRStorageUploadTask: validate content just before uploading (#2350)
* Calling stopFetching on GTMSeesionFetcher to stop callbacks from being called after deallocation.
Also fixing retain cycles in all task classes.
* Addressing build warnings
* Adjusting indentation