Add viewing of error messages from Keystone upon self-update failure.

chrome/browser/mac/keystone_glue.h

Index: chrome/browser/mac/keystone_glue.h
diff --git a/chrome/browser/mac/keystone_glue.h b/chrome/browser/mac/keystone_glue.h
index 912a1d9d116e8028c826e6cd353c7c96ed7e47ee..ff0de4a1f308c5223de1ccc7d42732d132a7a4f6 100644
--- a/chrome/browser/mac/keystone_glue.h
+++ b/chrome/browser/mac/keystone_glue.h
@@ -44,10 +44,12 @@ enum AutoupdateStatus {
 // the notification.  Its userInfo dictionary will contain an AutoupdateStatus
 // value as an intValue at key kAutoupdateStatusStatus.  If a version is
 // available (see AutoupdateStatus), it will be present at key
-// kAutoupdateStatusVersion.
+// kAutoupdateStatusVersion.  If any error messages were supplied by Keystone,
+// they will be present at key kAutoupdateStatusErrorMessages.
 extern NSString* const kAutoupdateStatusNotification;
 extern NSString* const kAutoupdateStatusStatus;
 extern NSString* const kAutoupdateStatusVersion;
+extern NSString* const kAutoupdateStatusErrorMessages;
 
 namespace {