Android Contacts application theme/style

Can you please tell me why the android Contacts application theme/style is using 'dark' theme? For example, the activity's background is Black instead of White. I have looked at their Android Manifest xml file and their layout xml file (e.g. call details.xml) file, but i don't see how they specified using a 'dark' theme?

Can you p开发者_JAVA百科lease tell me how do they do that? I have looked at http://developer.android.com/guide/topics/ui/themes.html, but I don't see Contacts app is doing that.

Thank you for any help.

The dark theme is the default in Android, if you do not specify otherwise.