Ensure that the referrer for HTTPS to HTTP downloads is dropped.

content/browser/download/url_downloader.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/download/url_downloader.h"
 
 #include "base/callback_helpers.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/threading/sequenced_task_runner_handle.h"
@@ skipping 49 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(RequestHandle);
 };
 
 // static
 std::unique_ptr<UrlDownloader> UrlDownloader::BeginDownload(
     base::WeakPtr<UrlDownloader::Delegate> delegate,
     std::unique_ptr<net::URLRequest> request,
     const Referrer& referrer,
     bool is_parallel_request) {
-  Referrer::SetReferrerForRequest(request.get(), referrer);
+  Referrer sanitized_referrer =
+      Referrer::SanitizeForRequest(request->url(), referrer);

[asanka, 2017/06/08 16:44:30]

Whoa. This step is pretty easy to miss.

[David Trainor- moved to gerrit, 2017/06/08 17:16:38]

Should we have a bool sanitize in SetReferrerForRequest?  That way callers have
to explicitly declare whether or not they want the sanitization?

[svaldez, 2017/06/08 18:26:07]

Hmm, it looks like most other callers sanitize it early in the pipeline, so most
wouldn't be calling for sanitization, but it might be useful just as a fallback
in case. Should that be a separate CL?

+  Referrer::SetReferrerForRequest(request.get(), sanitized_referrer);
 
   if (request->url().SchemeIs(url::kBlobScheme))
     return nullptr;
 
   // From this point forward, the |UrlDownloader| is responsible for
   // |started_callback|.
   std::unique_ptr<UrlDownloader> downloader(
       new UrlDownloader(std::move(request), delegate, is_parallel_request));
   downloader->Start();
 
@@ skipping 153 matching lines @@
 }
 
 void UrlDownloader::Destroy() {
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(&UrlDownloader::Delegate::OnUrlDownloaderStopped, delegate_,
                  this));
 }
 
 }  // namespace content