Origins should be represented as url::Origin (not as GURL).

As pointed out in //docs/security/origin-vs-url.md, origins should be
represented as url::Origin (not as GURL).  This CL applies this
guideline to predictor-related code and changes the type of the
following fields from GURL to url::Origin:
- OriginRequestSummary::origin
- PreconnectedRequestStats::origin
- PreconnectRequest::origin

The old code did not depend on any non-origin parts of GURL
(like path and/or query).  Therefore, this CL has no intended
behavior change.

Bug: 973885
Change-Id: Idd14590b4834cb9d50c74ed747b595fe1a4ba357
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1895167
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Reviewed-by: Alex Ilin <alexilin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#716311}
void PreconnectManager::StartPreresolveHosts(
    const std::vector<std::string>& hostnames) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  for (auto it = hostnames.rbegin(); it != hostnames.rend(); ++it) {
    PreresolveJobId job_id =
        preresolve_jobs_.Add(std::make_unique<PreresolveJob>(
            GURL("http://" + *it), 0, kAllowCredentialsOnPreconnectByDefault,
            net::NetworkIsolationKey(), nullptr));
    queued_jobs_.push_front(job_id);
  }

  TryToLaunchPreresolveJobs();
}

void PreconnectManager::StartPreresolveHosts(
    const std::vector<std::string>& hostnames) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  for (auto it = hostnames.rbegin(); it != hostnames.rend(); ++it) {
    PreresolveJobId job_id =
        preresolve_jobs_.Add(std::make_unique<PreresolveJob>(
            GURL("http://" + *it), 0, kAllowCredentialsOnPreconnectByDefault,
            net::NetworkIsolationKey(), nullptr));
    queued_jobs_.push_front(job_id);
  }

  TryToLaunchPreresolveJobs();
}
