Get the default device scale factor from monitor

ui/gfx/gfx_switches.cc

Index: ui/gfx/gfx_switches.cc
diff --git a/ui/gfx/gfx_switches.cc b/ui/gfx/gfx_switches.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6daf1c2d522b3d2a8c1c4b6e34888e1f3a5fa7e1
--- /dev/null
+++ b/ui/gfx/gfx_switches.cc
@@ -0,0 +1,13 @@
+// Copyright (c) 2012 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/gfx/gfx_switches.h"
+
+namespace switches {
+
+// The default device scale factor to apply to the browser UI and
+// the contents in the absence of a viewport meta tag.
+const char kDefaultDeviceScaleFactor[] = "default-device-scale-factor";
+
+}  // namespace switches