A little Googling turned up this (definitely not the original source, though):

https://github.com/CyanogenMod/android_external_strace/blob/...

  $ strace  -tt -q -o graph.strace -s 100 -f bash -c 'ls |wc -l'
  $ ./strace-graph graph.strace 
  bash -c ls |wc -l
    +-- ls
    `-- wc -l

The comments in the code claim it will show elapsed time for each process, but that's not working for me.

I discovered the Python ptrace module while I was searching for this. I have a project for which modifying the Python module might be a nice alternative to parsing strace output.