On the fsfs-format7 branch: fix check for containered base represenations.

* subversion/libsvn_fs_fs/cached_data.c
  (get_combined_window): check soure rep instead of current

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1490964 13f79535-47bb-0310-9956-ffa450edef68