Remove the WARNING security level.

ios/web/public/security_style.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IOS_WEB_PUBLIC_SECURITY_STYLE_H_
 #define IOS_WEB_PUBLIC_SECURITY_STYLE_H_
 
 namespace web {
 
 // Various aspects of the UI change their appearance according to the security
@@ skipping 10 matching lines @@
   // not be determined, either because it was retrieved using an unauthenticated
   // protocol, such as HTTP or FTP, or it was retrieved using a protocol that
   // supports authentication, such as HTTPS, but there were errors during
   // transmission that render us uncertain to the object's authenticity.
   SECURITY_STYLE_UNAUTHENTICATED,
 
   // SECURITY_STYLE_AUTHENTICATION_BROKEN indicates that we tried to retrieve
   // this object in an authenticated manner but were unable to do so.
   SECURITY_STYLE_AUTHENTICATION_BROKEN,
 
-  // SECURITY_STYLE_WARNING means that the object was retrieved in an
-  // authenticated manner, but there were security issues with the retrieval or
-  // the object interacted with less secure objects.
-  SECURITY_STYLE_WARNING,
-
   // SECURITY_STYLE_AUTHENTICATED indicates that we successfully retrieved this
   // object over an authenticated protocol, such as HTTPS.
   SECURITY_STYLE_AUTHENTICATED,
   SECURITY_STYLE_LAST = SECURITY_STYLE_AUTHENTICATED
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_SECURITY_STYLE_H_