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

ui/base/device_form_factor_ios.mm

Index: ui/base/device_form_factor_ios.mm
diff --git a/ui/base/device_form_factor_ios.mm b/ui/base/device_form_factor_ios.mm
new file mode 100644
index 0000000000000000000000000000000000000000..7974483a97da36c02dab260d7216b3295e8a0bbd
--- /dev/null
+++ b/ui/base/device_form_factor_ios.mm
@@ -0,0 +1,18 @@
+// 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"
+
+#import <UIKit/UIKit.h>
+
+namespace ui {
+
+DeviceFormFactor GetDeviceFormFactor() {
+  UIUserInterfaceIdiom idiom = [[UIDevice currentDevice] userInterfaceIdiom];

[noyau (Ping after 24h), 2013/11/05 15:48:03]

We currently use ios_ui_util::iPadIdiom() all over the place to to this check.

We should pick one or the other to contain the canonical implementation and have
the other one calling it. As the implementation in this file is cross-platform I
suggest changing ios_ui_util::iPadIdiom() to call it.

[Alexei Svitkine (slow), 2013/11/05 16:27:28]

Agreed. It will need to be done separately once this lands, since
ios_ui_util::iPadIdiom() is not in the upstream repo.

+  if (idiom == UIUserInterfaceIdiomPad)
+    return DEVICE_FORM_FACTOR_TABLET;
+  return DEVICE_FORM_FACTOR_PHONE;
+}
+
+}  // namespace ui