Add a benchmark with quite a high degree of fanout.
Add a benchmark with quite a high degree of fanout.

Change-Id: I6dc42c506498dac3ab650cd55cc9e052a439c804
Reviewed-on: https://code-review.googlesource.com/4500
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

google/re2,google/re2,google/re2,google/re2,google/re2