Remove the WARNING security level.

ios/chrome/browser/ssl/ios_chrome_security_state_model_client.mm

 // Copyright 2016 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.
 
 #include "ios/chrome/browser/ssl/ios_chrome_security_state_model_client.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "ios/web/public/navigation_item.h"
@@ skipping 16 matching lines @@
 security_state::SecurityStateModel::SecurityLevel
 GetSecurityLevelForSecurityStyle(web::SecurityStyle style) {
   switch (style) {
     case web::SECURITY_STYLE_UNKNOWN:
       NOTREACHED();
       return security_state::SecurityStateModel::NONE;
     case web::SECURITY_STYLE_UNAUTHENTICATED:
       return security_state::SecurityStateModel::NONE;
     case web::SECURITY_STYLE_AUTHENTICATION_BROKEN:
       return security_state::SecurityStateModel::SECURITY_ERROR;
-    case web::SECURITY_STYLE_WARNING:
-      // //ios/web currently doesn't use this style.
-      NOTREACHED();
-      return security_state::SecurityStateModel::SECURITY_WARNING;
     case web::SECURITY_STYLE_AUTHENTICATED:
       return security_state::SecurityStateModel::SECURE;
   }
   return security_state::SecurityStateModel::NONE;
 }
 
 }  // namespace
 
 IOSChromeSecurityStateModelClient::IOSChromeSecurityStateModelClient(
     web::WebState* web_state)
@@ skipping 43 matching lines @@
   state->initial_security_level =
       GetSecurityLevelForSecurityStyle(ssl.security_style);
   state->certificate = ssl.certificate;
   state->cert_status = ssl.cert_status;
   state->connection_status = ssl.connection_status;
   state->security_bits = ssl.security_bits;
   state->displayed_mixed_content =
       (ssl.content_status & web::SSLStatus::DISPLAYED_INSECURE_CONTENT) ? true
                                                                         : false;
 }