In the comments for this file there is a reference to gperftools
for more info on pprof. pprof now live on its own repo on github,
and the version in gperftools is deprecated.

Change-Id: I8a188f129534f73edd132ef4e5a2d566e69df7e9
Reviewed-on: https://go-review.googlesource.com/24502Reviewed-by: Ian Lance Taylor <iant@golang.org>