webRequest.onAuthRequired listeners can provide authentication credentials.

chrome/browser/extensions/extension_webrequest_api_constants.h

Index: chrome/browser/extensions/extension_webrequest_api_constants.h
diff --git a/chrome/browser/extensions/extension_webrequest_api_constants.h b/chrome/browser/extensions/extension_webrequest_api_constants.h
index 734cbd414895a76e0cd7f79df9f77e5b61fbb55b..15e34bf4d7f7d489520a4d033111a7ddc93970c1 100644
--- a/chrome/browser/extensions/extension_webrequest_api_constants.h
+++ b/chrome/browser/extensions/extension_webrequest_api_constants.h
@@ -35,6 +35,9 @@ extern const char kHeaderValueKey[];
 extern const char kIsProxyKey[];
 extern const char kSchemeKey[];
 extern const char kRealmKey[];
+extern const char kAuthCredentialsKey[];
+extern const char kUsernameKey[];
+extern const char kPasswordKey[];
 
 // Events.
 extern const char kOnAuthRequired[];