Warn user in case extension delays network traffic too much.

chrome/common/chrome_notification_types.h

Index: chrome/common/chrome_notification_types.h
diff --git a/chrome/common/chrome_notification_types.h b/chrome/common/chrome_notification_types.h
index 35d334901433a547b018172e949f5df2157bc636..0fb69fd569cf0238ca5618241038700820134ec5 100644
--- a/chrome/common/chrome_notification_types.h
+++ b/chrome/common/chrome_notification_types.h
@@ -515,6 +515,11 @@ enum NotificationType {
   // (const std::string).
   NOTIFICATION_EXTENSION_UPDATE_FOUND,
 
+  // Sent when one or more extensions changed their warning status (like
+  // slowing down Chrome or conflicting with each other).
+  // The source is a Profile.
+  NOTIFICATION_EXTENSION_WARNING_CHANGED,
+
   // An installed app changed notification state (added or removed
   // notifications). The source is a Profile, and the details are a string
   // with the extension id of the app.