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}
void Job::StartGetProxyForURL(const GURL& url,
                              ProxyInfo* results,
                              const CompletionCallback& callback) {
  CheckIsOnOriginThread();

  url_ = url;
  user_results_ = results;

  Start(GET_PROXY_FOR_URL, false /*non-blocking*/, callback);
}

void Job::StartGetProxyForURL(const GURL& url,
                              ProxyInfo* results,
                              const CompletionCallback& callback) {
  CheckIsOnOriginThread();

  url_ = url;
  user_results_ = results;

  Start(GET_PROXY_FOR_URL, false /*non-blocking*/, callback);
}
