In addition to the "goroutine" and "threadcreate" profiles,
Go code can generate custom profiles using the runtime/pprof package.
The user must name these profiles, and the docs recommend using the
convention "import/path" to avoid namespace conflicts.  This CL
updates the pprof tool to be able to parse legacy profiles whose types
contain slashes and other non-space characters.

This is the upstream fix for https://github.com/golang/go/issues/13195.
This change will need to be mirrored to
github.com/golang/go/src/cmd/pprof/internal/profile/legacy_profile.go