Fix incorrect RequestPriority to SpdyPriority conversion

https://crrev.com/c/1343047 incorrectly used
ConvertRequestPriorityToSpdyPriority when it should have used
ConvertRequestPriorityToQuicPriority when setting the priority of a
QuicProxyClientSocket.

Bug: 166689
Change-Id: I82fd9e9b0a851df1fce4450172d320f554cf379c
Reviewed-on: https://chromium-review.googlesource.com/c/1362183Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613756}

net/quic/quic_proxy_client_socket.cc

@@ -16,6 +16,7 @@
 #include "net/http/proxy_connect_redirect_http_stream.h"
 #include "net/log/net_log_source.h"
 #include "net/log/net_log_source_type.h"
+#include "net/quic/quic_http_utils.h"
 #include "net/spdy/spdy_http_utils.h"
 #include "net/traffic_annotation/network_traffic_annotation.h"
 
@@ -87,7 +88,7 @@ NextProto QuicProxyClientSocket::GetProxyNegotiatedProtocol() const {
 }
 
 void QuicProxyClientSocket::SetStreamPriority(RequestPriority priority) {
-  stream_->SetPriority(ConvertRequestPriorityToSpdyPriority(priority));
+  stream_->SetPriority(ConvertRequestPriorityToQuicPriority(priority));
 }
 
 // Sends a HEADERS frame to the proxy with a CONNECT request