Implement simple http server with set cookie functionality.

ios/web/public/test/http_server_util.mm

Index: ios/web/public/test/http_server_util.mm
diff --git a/ios/web/public/test/http_server_util.mm b/ios/web/public/test/http_server_util.mm
index 7b032bcc81613bfa3d15caddaf9bd50b048687b4..ed9ae78988698131b581b4c5c9cf227aa0742a5b 100644
--- a/ios/web/public/test/http_server_util.mm
+++ b/ios/web/public/test/http_server_util.mm
@@ -17,6 +17,12 @@ void SetUpSimpleHttpServer(const std::map<GURL, std::string>& responses) {
   SetUpHttpServer(base::MakeUnique<HtmlResponseProvider>(responses));
 }
 
+void SetUpSimpleHttpServerWithSetCookie(
+    const std::map<GURL, std::string>& responses,
+    const std::string& cookie) {
+  SetUpHttpServer(base::MakeUnique<HtmlResponseProvider>(responses, cookie));
+}
+
 void SetUpFileBasedHttpServer() {
   base::FilePath path;
   PathService::Get(base::DIR_MODULE, &path);