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

ui/base/device_form_factor_android.cc

Index: ui/base/device_form_factor_android.cc
diff --git a/ui/base/device_form_factor_android.cc b/ui/base/device_form_factor_android.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3c9763f39fea31094aa1ff39c5c23ca9284b17f9
--- /dev/null
+++ b/ui/base/device_form_factor_android.cc
@@ -0,0 +1,15 @@
+// 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 "device_form_factor.h"
+
+#include "base/command_line.h"
+#include "ui_base_switches.h"
+
+DeviceFormFactor GetDeviceFormFactor() {
+  if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kTabletUI)) {
+    return DEVICE_FORM_FACTOR_TABLET;
+  }
+  return DEVICE_FORM_FACTOR_PHONE;
+}