Add more options to --screen-config flag.

ui/display/types/display_mode.h

 // 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.
 
 #ifndef UI_DISPLAY_TYPES_DISPLAY_MODE_H_
 #define UI_DISPLAY_TYPES_DISPLAY_MODE_H_
 
 #include <memory>
+#include <ostream>
 #include <string>
 
 #include "base/macros.h"
 #include "ui/display/types/display_types_export.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace ui {
 
 // This class represents the basic information for a native mode. Platforms will
 // extend this class to add platform specific information about the mode.
@@ skipping 10 matching lines @@
   virtual std::string ToString() const;
 
  private:
   gfx::Size size_;
   bool is_interlaced_;
   float refresh_rate_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayMode);
 };
 
+// Used to by gtest to print readable errors.
+DISPLAY_TYPES_EXPORT void PrintTo(const DisplayMode& mode, std::ostream* os);
+
 }  // namespace ui
 
 #endif  // UI_DISPLAY_TYPES_DISPLAY_MODE_H_