Add policy domain for signin screen apps

components/policy/core/common/policy_namespace.h

Index: components/policy/core/common/policy_namespace.h
diff --git a/components/policy/core/common/policy_namespace.h b/components/policy/core/common/policy_namespace.h
index 3a7424ed3982eb1600bf271e2fc95d5edabcb6a1..d3d70506fef0a951ea12966182da2bd7aa6a31b3 100644
--- a/components/policy/core/common/policy_namespace.h
+++ b/components/policy/core/common/policy_namespace.h
@@ -26,6 +26,11 @@ enum PolicyDomain {
   // The component ID for the extension policies is equal to the extension ID.
   POLICY_DOMAIN_EXTENSIONS,
 
+  // The namespace that corresponds to the policies for extensions running
+  // under Chrome OS signin profile. The component ID is equal to the extension
+  // ID.
+  POLICY_DOMAIN_SIGNIN_EXTENSIONS,
+
   // Must be the last entry.
   POLICY_DOMAIN_SIZE,
 };