Add cross-platform API to get the form factor of the device

ui/base/device_form_factor_desktop.cc

Index: ui/base/device_form_factor_desktop.cc
diff --git a/ui/base/device_form_factor_desktop.cc b/ui/base/device_form_factor_desktop.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2f74015309df824f21bdcb5a61ba2a77b711d29f
--- /dev/null
+++ b/ui/base/device_form_factor_desktop.cc
@@ -0,0 +1,13 @@
+// Copyright 2013 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/base/device_form_factor.h"
+
+namespace ui {
+
+DeviceFormFactor GetDeviceFormFactor() {
+  return DEVICE_FORM_FACTOR_DESKTOP;
+}
+
+}  // namespace ui