Add a constraint on how many requests can be outstanding for any given render (browser-side).

net/url_request/url_request.cc

Index: net/url_request/url_request.cc
===================================================================
--- net/url_request/url_request.cc	(revision 9239)
+++ net/url_request/url_request.cc	(working copy)
@@ -234,10 +234,6 @@
 void URLRequest::CancelWithError(int os_error) {
   DCHECK(os_error < 0);
 
-  // There's nothing to do if we are not waiting on a Job.
-  if (!is_pending_ || !job_)
-    return;
-
   // If the URL request already has an error status, then canceling is a no-op.
   // Plus, we don't want to change the error status once it has been set.
   if (status_.is_success()) {
@@ -245,6 +241,10 @@
     status_.set_os_error(os_error);
   }
 
+  // There's nothing to do if we are not waiting on a Job.
+  if (!is_pending_ || !job_)
+    return;
+
   job_->Kill();
 
   // The Job will call our NotifyDone method asynchronously.  This is done so
@@ -350,7 +350,7 @@
     method_ = "GET";
   }
   url_ = location;
-  upload_ = 0;
+  upload_ = NULL;
   status_ = URLRequestStatus();
   --redirect_limit_;