Add WritePushPromise() method in QuicHeadersStream for server push.

net/quic/quic_headers_stream.h

Index: net/quic/quic_headers_stream.h
diff --git a/net/quic/quic_headers_stream.h b/net/quic/quic_headers_stream.h
index 6cf7c7df2f45f9cc9b71ad202134453aa3a25c45..ef1bfef841c11177c7af8500a523fdf358eac01a 100644
--- a/net/quic/quic_headers_stream.h
+++ b/net/quic/quic_headers_stream.h
@@ -33,7 +33,15 @@ class NET_EXPORT_PRIVATE QuicHeadersStream : public ReliableQuicStream {
                       const SpdyHeaderBlock& headers,
                       bool fin,
                       SpdyPriority priority,
-                      QuicAckListenerInterface* ack_notifier_delegate);
+                      QuicAckListenerInterface* ack_listener);
+
+  // Write |headers| for |promised_stream_id| on |original_stream_id| in a
+  // PUSH_PROMISE frame to peer. Return the size, in bytes, of the resulting
+  // SPDY frame.
+  size_t WritePushPromise(QuicStreamId original_stream_id,
+                          QuicStreamId promised_stream_id,
+                          const SpdyHeaderBlock& headers,
+                          QuicAckListenerInterface* ack_listener);
 
   // ReliableQuicStream implementation
   void OnDataAvailable() override;