Abstract most Profile knowledge from SigninManager.

components/signin/core/common/signin_pref_names.cc

Index: components/signin/core/common/signin_pref_names.cc
diff --git a/components/signin/core/common/signin_pref_names.cc b/components/signin/core/common/signin_pref_names.cc
index ec303ff1b3864b68d8b45f21d590c2da61a330de..0388fdc0703f0944f7fde6ae0dc2305724419140 100644
--- a/components/signin/core/common/signin_pref_names.cc
+++ b/components/signin/core/common/signin_pref_names.cc
@@ -20,6 +20,12 @@ const char kGoogleServicesUserAccountId[] = "google.services.user_account_id";
 // services.
 const char kGoogleServicesUsername[] = "google.services.username";
 
+// Local state pref containing a string regex that restricts which accounts
+// can be used to log in to chrome (e.g. "*@google.com"). If missing or blank,
+// all accounts are allowed (no restrictions).
+const char kGoogleServicesUsernamePattern[] =
+    "google.services.username_pattern";
+
 // Boolean which stores if the user is allowed to signin to chrome.
 const char kSigninAllowed[] = "signin.allowed";