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..37aba0277640290120f56cc47248806b9ca74648 100644
--- a/net/url_request/url_fetcher.h
+++ b/net/url_request/url_fetcher.h
@@ -186,13 +186,21 @@ class NET_EXPORT URLFetcher {
   // after backoff_delay() elapses. URLFetcher has it set to true by default.
   virtual void SetAutomaticallyRetryOn5xx(bool retry) = 0;
 
-  virtual void SetMaxRetries(int max_retries) = 0;
-  virtual int GetMaxRetries() const = 0;
+  virtual void SetMaxRetriesOn5xx(int max_retries) = 0;
+  virtual int GetMaxRetriesOn5xx() const = 0;
 
   // Returns the back-off delay before the request will be retried,
   // 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. The first fetch is also
+  // delayed if the network is offline when Start() is invoked.
+  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.