Replace QuicAckListenerInterface* with scoped_refptr<QuicAckListenerInterface>.

net/quic/core/quic_spdy_session.h

Index: net/quic/core/quic_spdy_session.h
diff --git a/net/quic/core/quic_spdy_session.h b/net/quic/core/quic_spdy_session.h
index 4da806ac45ab83272574ddb6d435e48ef27fa907..fd4958843dbb4e0e6bf1745c6d354f5e9f737dea 100644
--- a/net/quic/core/quic_spdy_session.h
+++ b/net/quic/core/quic_spdy_session.h
@@ -60,11 +60,12 @@ class QUIC_EXPORT_PRIVATE QuicSpdySession : public QuicSession {
   // If |fin| is true, then no more data will be sent for the stream |id|.
   // If provided, |ack_notifier_delegate| will be registered to be notified when
   // we have seen ACKs for all packets resulting from this call.
-  virtual size_t WriteHeaders(QuicStreamId id,
-                              SpdyHeaderBlock headers,
-                              bool fin,
-                              SpdyPriority priority,
-                              QuicAckListenerInterface* ack_notifier_delegate);
+  virtual size_t WriteHeaders(
+      QuicStreamId id,
+      SpdyHeaderBlock headers,
+      bool fin,
+      SpdyPriority priority,
+      const scoped_refptr<QuicAckListenerInterface>& ack_notifier_delegate);
 
   QuicHeadersStream* headers_stream() { return headers_stream_.get(); }