Optimize smoke tests to skip iterations

  # TODO(crbug.com/894254): Add flag to reduce iterations to 1.
  # (An iteration is a repeat of the benchmark without restarting Chrome. It
  # must be supported in benchmark-specific code.)'). This supports the smoke
  # test use case since we don't want to waste time with iterations in smoke
  # tests.

This would help with the FindIt use case described in issue 894254.

detailed doc is at https://goo.gl/JZ2yZQ