Add Active Directory login UI tests

chrome/browser/chromeos/login/helper.h

Index: chrome/browser/chromeos/login/helper.h
diff --git a/chrome/browser/chromeos/login/helper.h b/chrome/browser/chromeos/login/helper.h
index cd27dc773f406c356b6cb5c9acee4a50aa2882fd..39c169d2a7f8646d81ef39f5cb2b6996107b64cc 100644
--- a/chrome/browser/chromeos/login/helper.h
+++ b/chrome/browser/chromeos/login/helper.h
@@ -42,6 +42,16 @@ int GetCurrentUserImageSize();
 // conflict with other chromeos components.
 namespace login {
 
+// Possible error states of the Active Directory screen. Must be in the same
+// order as ACTIVE_DIRECTORY_ERROR_STATE enum values.
+enum class ActiveDirectoryErrorState {
+  NONE = 0,

[Thiemo Nagel, 2017/03/21 13:44:22]

Nit: "SUCCESS" might be easier to understand?

[Roman Sorokin (ftl), 2017/03/22 15:19:25]

I'm not sure it's less confusing. We don't have any 'success' state. Just the
default NONE error one.

+  MACHINE_NAME_INVALID = 1,
+  MACHINE_NAME_TOO_LONG = 2,
+  BAD_USERNAME = 3,
+  BAD_PASSWORD = 4,
+};
+
 // Maximum size of user image, in which it should be saved to be properly
 // displayed under all possible DPI values.
 const int kMaxUserImageSize = 512;