Client-side changes to support retry GU.

sync/sessions/sync_session.h

Index: sync/sessions/sync_session.h
diff --git a/sync/sessions/sync_session.h b/sync/sessions/sync_session.h
index f5767206d2a1bb122c81bd554739cc35f65a01c9..9841a58b2d8ac4334acfb8954e0f80f25d3f6cf5 100644
--- a/sync/sessions/sync_session.h
+++ b/sync/sessions/sync_session.h
@@ -81,6 +81,9 @@ class SYNC_EXPORT_PRIVATE SyncSession {
     // will buffer locally.
     virtual void OnReceivedClientInvalidationHintBufferSize(int size) = 0;
 
+    // Called when server wants to schedule a retry GU.
+    virtual void OnReceivedGuRetryDelaySeconds(int delay_seconds) = 0;
+
    protected:
     virtual ~Delegate() {}
   };