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

net/spdy/spdy_session_pool.h

Index: net/spdy/spdy_session_pool.h
diff --git a/net/spdy/spdy_session_pool.h b/net/spdy/spdy_session_pool.h
index b77f28bc40787c5e3ad8706f9f96932ab1360e4b..0467583eefa0f8ea73936c0adbadc51d79ad58b9 100644
--- a/net/spdy/spdy_session_pool.h
+++ b/net/spdy/spdy_session_pool.h
@@ -104,9 +104,9 @@ class NET_EXPORT SpdySessionPool
   // Close all SpdySessions, including any new ones created in the process of
   // closing the current ones.
   void CloseAllSessions();
-  // Close only the currently existing SpdySessions. Let any new ones created
-  // continue to live.
-  void CloseCurrentSessions();
+  // Close only the currently existing SpdySessions with |error|.
+  // Let any new ones created continue to live.
+  void CloseCurrentSessions(net::Error error);
   // Close only the idle SpdySessions.
   void CloseIdleSessions();