@Override
          public int compare(DefaultDiskStorage.Entry a, DefaultDiskStorage.Entry b) {
            long al = a.getTimestamp();
            long bl = b.getTimestamp();
            return (al < bl) ? -1 : ((al > bl) ? 1 : 0);
          }
Retrieves a list of entries (the one returned by DiskStorage.Session.entriesIterator) ordered
by timestamp.

@param storage
imagepipeline-base/src/test/java/com/facebook/cache/disk/DefaultDiskStorageTest.java