webui cert manager: Add specific error message for importing a cert twice.

chrome/browser/ui/webui/options2/certificate_manager_handler2.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/webui/options2/certificate_manager_handler2.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/file_util.h"  // for FileAccessProvider
 #include "base/memory/scoped_vector.h"
@@ skipping 116 matching lines @@
   }
 
   icu::Collator* collator_;
 };
 
 std::string NetErrorToString(int net_error) {
   switch (net_error) {
     // TODO(mattm): handle more cases.
     case net::ERR_IMPORT_CA_CERT_NOT_CA:
       return l10n_util::GetStringUTF8(IDS_CERT_MANAGER_ERROR_NOT_CA);
+    case net::ERR_IMPORT_CERT_ALREADY_EXISTS:
+      return l10n_util::GetStringUTF8(
+          IDS_CERT_MANAGER_ERROR_CERT_ALREADY_EXISTS);
     default:
       return l10n_util::GetStringUTF8(IDS_CERT_MANAGER_UNKNOWN_ERROR);
   }
 }
 
 }  // namespace
 
 namespace options2 {
 
 ///////////////////////////////////////////////////////////////////////////////
@@ skipping 907 matching lines @@
   web_ui()->CallJavascriptFunction("CertificateManager.onCheckTpmTokenReady",
                                    ready);
 }
 #endif
 
 gfx::NativeWindow CertificateManagerHandler::GetParentWindow() const {
   return web_ui()->GetWebContents()->GetView()->GetTopLevelNativeWindow();
 }
 
 }  // namespace options2