Allow proxying plaintext websockets over http/2 proxy

net/http/http_stream_factory_impl_job.cc

Index: net/http/http_stream_factory_impl_job.cc
diff --git a/net/http/http_stream_factory_impl_job.cc b/net/http/http_stream_factory_impl_job.cc
index 2cd3bcbe0b6c7cf73b0129896405537a9a92cfcb..de46c194450d0273400e353ef26a7555d0b7e12c 100644
--- a/net/http/http_stream_factory_impl_job.cc
+++ b/net/http/http_stream_factory_impl_job.cc
@@ -1164,8 +1164,17 @@ int HttpStreamFactoryImpl::Job::DoCreateStream() {
   if (connection_->socket() && !connection_->is_reused())
     SetSocketMotivation();
 
-  if (!using_spdy_) {
+  if (!using_spdy_)
     DCHECK(!IsSpdyAlternative());
+
+  if (!using_spdy_ ||
+      // While websockets over HTTP/2 are not supported, it is still valid to
+      // have websockets tunneled over HTTP/2 proxy (via CONNECT). If websockets
+      // are secure (wss://), HttpProxyClientSocket with established tunnel is
+      // wrapped with yet another socket (SSLClientSocket), and |using_spdy_|
+      // will be false, but for ws: scheme, HttpProxyClientSocket won't be
+      // wrapped into anything.
+      (using_spdy_ && proxy_info_.is_https() && delegate_->for_websockets())) {
     // We may get ftp scheme when fetching ftp resources through proxy.
     bool using_proxy = (proxy_info_.is_http() || proxy_info_.is_https()) &&
                        (request_info_.url.SchemeIs(url::kHttpScheme) ||