Add an extension override bubble and warning box for proxy extensions.

extensions/browser/extension_prefs.h

Index: extensions/browser/extension_prefs.h
diff --git a/extensions/browser/extension_prefs.h b/extensions/browser/extension_prefs.h
index 069b60481cff79e44581dbfdbfc803d1d89d05ad..50bb03b8b28b4bf7fe865bb1b72b515ce4ba1713 100644
--- a/extensions/browser/extension_prefs.h
+++ b/extensions/browser/extension_prefs.h
@@ -329,6 +329,13 @@ class ExtensionPrefs : public ExtensionScopedPrefs, public KeyedService {
   void SetNtpOverriddenBubbleBeenAcknowledged(const std::string& extension_id,
                                               bool value);
 
+  // Whether the user has been notified about extension with |extension_id|
+  // overriding the proxy.
+  bool HasProxyOverriddenBubbleBeenAcknowledged(
+      const std::string& extension_id);
+  void SetProxyOverriddenBubbleBeenAcknowledged(const std::string& extension_id,
+                                                bool value);
+
   // Returns true if the extension notification code has already run for the
   // first time for this profile. Currently we use this flag to mean that any
   // extensions that would trigger notifications should get silently