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

content/browser/download/url_downloader.cc

Index: content/browser/download/url_downloader.cc
diff --git a/content/browser/download/url_downloader.cc b/content/browser/download/url_downloader.cc
index c20669db6911a00e11a3b94f1c1b06ee1bd49508..c35c1e7c842a41050c09c7ccab8f770668ab42a6 100644
--- a/content/browser/download/url_downloader.cc
+++ b/content/browser/download/url_downloader.cc
@@ -67,7 +67,9 @@ std::unique_ptr<UrlDownloader> UrlDownloader::BeginDownload(
     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;