Added callback to DownloadUrl() so we can find download failures.

net/url_request/url_request.h

 // Copyright (c) 2012 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.
 
 #ifndef NET_URL_REQUEST_URL_REQUEST_H_
 #define NET_URL_REQUEST_URL_REQUEST_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 306 matching lines @@
   // See switches::kEnableMacCookies.
   static void EnableMacCookies();
   static bool AreMacCookiesEnabled();
 
   // The original url is the url used to initialize the request, and it may
   // differ from the url if the request was redirected.
   const GURL& original_url() const { return url_chain_.front(); }
   // The chain of urls traversed by this request.  If the request had no
   // redirects, this vector will contain one element.
   const std::vector<GURL>& url_chain() const { return url_chain_; }
-  const GURL& url() const { return url_chain_.back(); }
+  const GURL& url() const {

[cbentzel, 2012/03/08 17:58:48]

Why was this change needed?

[ahendrickson, 2012/03/08 21:33:07]

I was getting a crash because url_chain_ was empty in some test.

[Randy Smith (Not in Mondays), 2012/03/09 19:14:02]

Did you look at why it was empty in those tests when it wasn't before?  I
dislike making production code changes for tests, and I wouldn't have thought
that this CL would result in a change in url_chain_ contents.  And we don't
really have a url_request.h expert on the review list (excepting possibly Chris
:-}).  "If you don't understand it, it's dangerous."

[ahendrickson, 2012/03/09 20:50:08]

No, I didn't.

I've reverted this, and will see if I can reproduce it.

+    return url_chain_.size() ? url_chain_.back() : GURL::EmptyGURL();
+  }
 
   // The URL that should be consulted for the third-party cookie blocking
   // policy.
   const GURL& first_party_for_cookies() const {
     return first_party_for_cookies_;
   }
   // This method may be called before Start() or FollowDeferredRedirect() is
   // called.
   void set_first_party_for_cookies(const GURL& first_party_for_cookies);
 
@@ skipping 432 matching lines @@
   scoped_refptr<AuthChallengeInfo> auth_info_;
 
   base::TimeTicks creation_time_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequest);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_H_