Remove FD optimization case for decodeStream

 Bug: 10677727
 The problem is that the FileInputStream may be wrapping a pipe or
 AssetFileDescriptor which fails if handed to decodeFileDescriptor.
 The problem is that AFDs can start in the middle of a file, whereas
 decodeFileDescriptor assumes it can mmap() the FD and start at
 the beginning.

Change-Id: I98a3c5f789865145e25a99b32d205e290808c1cf