Add more options to --screen-config flag.

ui/display/types/display_mode.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/display/types/display_mode.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/stringprintf.h"
 
 namespace ui {
@@ skipping 14 matching lines @@
 }
 
 std::string DisplayMode::ToString() const {
   return base::StringPrintf("[%dx%d %srate=%f]",
                             size_.width(),
                             size_.height(),
                             is_interlaced_ ? "interlaced " : "",
                             refresh_rate_);
 }
 
+void PrintTo(const DisplayMode& mode, std::ostream* os) {
+  *os << mode.ToString();
+}
+
 }  // namespace ui