driver: don't use runtime/trace < Go 1.5

Currently the benchmark driver does not build prior to Go 1.5 because
it uses runtime/trace, which was added in Go 1.5. Fix this by moving
the code to start and stop tracing to a version-gated source file.

Change-Id: I3267e496ad7af80ce4fd31fa653b86206df672e1
Reviewed-by: Dmitry Vyukov <>
2 files changed