Allow use of Mojo/V8 ProxyResolvers with URLRequestContextBuilder.

net/test/embedded_test_server/http_request.cc

Index: net/test/embedded_test_server/http_request.cc
diff --git a/net/test/embedded_test_server/http_request.cc b/net/test/embedded_test_server/http_request.cc
index ef624dcc8b052f94cabbb509642c64cf638e57ae..ecac8800f1248a80f2463c7c5e4be615b9f572c0 100644
--- a/net/test/embedded_test_server/http_request.cc
+++ b/net/test/embedded_test_server/http_request.cc
@@ -110,7 +110,7 @@ HttpRequestParser::ParseResult HttpRequestParser::ParseHeaders() {
     // know) anything about the server address.
     GURL url(header_line_tokens[1]);
     if (url.is_valid()) {
-      http_request_->relative_url = url.path();
+      http_request_->relative_url = url.PathForRequest();

[mmenke, 2017/05/12 17:19:40]

This was removing the query string, so breaking the use of echoheader (The other
cases here keep the query string)

     } else if (header_line_tokens[1][0] == '/') {
       http_request_->relative_url = header_line_tokens[1];
     } else {