imageBytes against the golden file identified by
The returned future completes with a boolean value that indicates whether
imageBytes matches the golden file's bytes within the tolerance defined
by the comparator.
In the case of comparison mismatch, the comparator may choose to throw a TestFailure if it wants to control the failure message.
The method by which
golden is located and by which its bytes are loaded
is left up to the implementation class. For instance, some implementations
may load files from the local file system, whereas others may load files
over the network or from a remote repository.
Future<bool> compare(Uint8List imageBytes, Uri golden);