Add support to URLRequest for deferring redirects....

net/url_request/url_request.h

Index: net/url_request/url_request.h
===================================================================
--- net/url_request/url_request.h	(revision 21335)
+++ net/url_request/url_request.h	(working copy)
@@ -135,10 +135,18 @@
     //
     // When this function is called, the request will still contain the
     // original URL, the destination of the redirect is provided in 'new_url'.
-    // If the request is not canceled the redirect will be followed and the
-    // request's URL will be changed to the new URL.
+    // If the delegate does not cancel the request and |*defer_redirect| is
+    // false, then the redirect will be followed, and the request's URL will be
+    // changed to the new URL.  Otherwise if the delegate does not cancel the
+    // request and |*defer_redirect| is true, then the redirect will be
+    // followed once FollowDeferredRedirect is called on the URLRequest.
+    //
+    // The default value for |*defer_redirect| is false, so that consumers do

[wtc, 2009/07/23 00:30:12]

I suggest rewriting this sentence as follows:

  The caller must set |*defer_redirect| to false, so that
  delegates do not need to set it if they are happy with the
  default behavior of not deferring redirect.

I also considered suggesting that this method returns
bool to indicate whether the redirect is deferred, but
I see that all the Delegate methods return void.  If
it's okay for a Delegate method to return non-void,
I think returning bool or an enum would be more clear.

[darin (slow to review), 2009/07/23 01:27:29]

Done.
I originally considered returning a bool, but I decided against it since it was
not so clear if returning false meant canceling the redirect or deferring the
redirect.  An enum would also make that clear, but an out parameter also makes
things more clear.

I'll think on the enum idea a bit more.

[wtc, 2009/07/23 02:37:48]

I agree.

+    // not need to set it if they are happy with the default behavior.
     virtual void OnReceivedRedirect(URLRequest* request,
-                                    const GURL& new_url) = 0;
+                                    const GURL& new_url,
+                                    bool* defer_redirect) {
+    }
 
     // Called when we receive an authentication failure.  The delegate should
     // call request->SetAuth() with the user's credentials once it obtains them,
@@ -436,6 +444,10 @@
   // will be set to an error.
   bool Read(net::IOBuffer* buf, int max_bytes, int *bytes_read);
 
+  // This method may be called to follow a redirect that was deferred in
+  // response to an OnReceivedRedirect call.
+  void FollowDeferredRedirect();
+
   // One of the following two methods should be called in response to an
   // OnAuthRequired() callback (and only then).
   // SetAuth will reissue the request with the given credentials.
@@ -494,7 +506,7 @@
   int Redirect(const GURL& location, int http_status_code);
 
   // Called by URLRequestJob to allow interception when a redirect occurs.
-  void ReceivedRedirect(const GURL& location);
+  void ReceivedRedirect(const GURL& location, bool* defer_redirect);
 
   // Called by URLRequestJob to allow interception when the final response
   // occurs.