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

chrome/common/form_factor.h

Index: chrome/common/form_factor.h
diff --git a/chrome/common/form_factor.h b/chrome/common/form_factor.h
new file mode 100644
index 0000000000000000000000000000000000000000..6c778d2ff46d862fa2a3793d37f8496a851fb4c2
--- /dev/null
+++ b/chrome/common/form_factor.h
@@ -0,0 +1,14 @@
+// Copyright

[Alexei Svitkine (slow), 2013/10/29 15:26:21]

Use the following copyright blob (in all the files):

// 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.

[yao, 2013/10/29 19:21:57]

Done.

+
+#ifndef CHROME_COMMON_FORM_FACTOR_H_
+#define CHROME_COMMON_FORM_FACTOR_H_
+
+enum Study_FormFactor {

[Alexei Svitkine (slow), 2013/10/29 15:26:21]

This should be a different enum than the variations Study protobuf ones.

Let's use the following names:

enum DeviceFormFactor {
  DEVICE_FORM_FACTOR_DESKTOP,
  DEVICE_FORM_FACTOR_PHONE,
  DEVICE_FORM_FACTOR_TABLET,
};

DeviceFormFactor GetDeviceFormFactor();

Also, change the files to chrome/common/device_form_factor*

(Sorry for changing my mind here since I originally told you to just use
form_factor* names).

[yao, 2013/10/29 19:21:57]

Done.

+  Study_FormFactor_DESKTOP = 0,
+  Study_FormFactor_PHONE = 1,
+  Study_FormFactor_TABLET = 2
+};
+
+Study_FormFactor GetFormFactor();

[Alexei Svitkine (slow), 2013/10/29 15:26:21]

Needs a comment. Mention that on non-Android, non-IOS platforms,
DEVICE_FORM_FACTOR_DESKTOP is always returned.

[yao, 2013/10/29 19:21:57]

Done.

+
+#endif  // CHROME_COMMON_FORM_FACTOR_H_