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/cocoa/flipped_view.mm b/ui/base/device_form_factor_desktop.cc
similarity index 60%
copy from ui/base/cocoa/flipped_view.mm
copy to ui/base/device_form_factor_desktop.cc
index 57c16477a94b7b30f709bc71abbe10fe009b4ee8..cfe56eae84fc413eaf8208b9cb733798eae2bfb1 100644
--- a/ui/base/cocoa/flipped_view.mm
+++ b/ui/base/device_form_factor_desktop.cc
@@ -2,12 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#import "ui/base/cocoa/flipped_view.h"
+#include "device_form_factor.h"
 
-@implementation FlippedView
-
-- (BOOL)isFlipped {
-  return YES;
+DeviceFormFactor GetDeviceFormFactor() {
+  return DEVICE_FORM_FACTOR_DESKTOP;
 }
-
-@end