Introduce ERR_NETWORK_CHANGED and allow URLFetcher to automatically retry on that error.

net/url_request/url_fetcher.h

Index: net/url_request/url_fetcher.h
diff --git a/net/url_request/url_fetcher.h b/net/url_request/url_fetcher.h
index 190e53932652eaa46f6a3450cc207b968c0ab97e..ca118c2f7202a104765972f0114f5ff0443b396a 100644
--- a/net/url_request/url_fetcher.h
+++ b/net/url_request/url_fetcher.h
@@ -193,6 +193,13 @@ class NET_EXPORT URLFetcher {
   // when a 5xx response was received.
   virtual base::TimeDelta GetBackoffDelay() const = 0;
 
+  // Retries up to |max_retries| times when requests fail with
+  // ERR_NETWORK_CHANGED. If ERR_NETWORK_CHANGED is received after having
+  // retried |max_retries| times then it is propagated to the observer.
+  // Each retry can be delayed if the network if currently offline, and will be
+  // attempted once the network connection is back.
+  virtual void SetAutomaticallyRetryOnNetworkChanges(int max_retries) = 0;
+
   // By default, the response is saved in a string. Call this method to save the
   // response to a file instead. Must be called before Start().
   // |file_task_runner| will be used for all file operations.