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::StartPreconnectUrl(
    const GURL& url,
    bool allow_credentials,
    net::NetworkIsolationKey network_isolation_key) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (!url.SchemeIsHTTPOrHTTPS())
    return;
  PreresolveJobId job_id = preresolve_jobs_.Add(std::make_unique<PreresolveJob>(
      url.GetOrigin(), 1, allow_credentials, std::move(network_isolation_key),
      nullptr));
  queued_jobs_.push_front(job_id);

  TryToLaunchPreresolveJobs();
}

void PreconnectManager::StartPreconnectUrl(
    const GURL& url,
    bool allow_credentials,
    net::NetworkIsolationKey network_isolation_key) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (!url.SchemeIsHTTPOrHTTPS())
    return;
  PreresolveJobId job_id = preresolve_jobs_.Add(std::make_unique<PreresolveJob>(
      url.GetOrigin(), 1, allow_credentials, std::move(network_isolation_key),
      nullptr));
  queued_jobs_.push_front(job_id);

  TryToLaunchPreresolveJobs();
}
