Add a histogram (Net.PacResultForStrippedUrl) that estimates how often PAC scripts depend on the URL path.

BUG=593759

Review URL: https://codereview.chromium.org/1797313003

Cr-Commit-Position: refs/heads/master@{#382644}
HostResolver* Job::host_resolver() {
  return bindings_->GetHostResolver();
}

HostResolver* Job::host_resolver() {
  return bindings_->GetHostResolver();
}
