Revert "seq_file: finish removal of len."

This reverts commit 736f970ccb5f7753a57773ae452eddeab3a9797a.
Revert "Merge remote-tracking branch 'caf/kk_2.7_rb1.43' into cm-11.0"

This reverts commit 8a0c2b63872ca442c2098f63dc9054d6a4d4a739, reversing
changes made to 76b191e0e5abfe59c9a957783c2f4d84390aaad1.