Componentize SigninIdAccountHelper.

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 97255bfb60b6ca0e510079a59e9d48132e69555c..ec303ff1b3864b68d8b45f21d590c2da61a330de 100644
--- a/components/signin/core/common/signin_pref_names.cc
+++ b/components/signin/core/common/signin_pref_names.cc
@@ -12,6 +12,10 @@ namespace prefs {
 // be the same.
 const char kGoogleServicesLastUsername[] = "google.services.last_username";
 
+// Obfuscated account ID that identifies the current user logged into sync and
+// other google services.
+const char kGoogleServicesUserAccountId[] = "google.services.user_account_id";
+
 // String that identifies the current user logged into sync and other google
 // services.
 const char kGoogleServicesUsername[] = "google.services.username";