Fix a crash in the Extension Creator when crx is in use.

chrome/browser/extensions/extension_creator.cc

 // Copyright (c) 2011 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/extensions/extension_creator.h"
 
 #include <string>
 #include <vector>
 
 #include "base/file_util.h"
@@ skipping 174 matching lines @@
   return true;
 }
 
 bool ExtensionCreator::WriteCRX(const FilePath& zip_path,
                                 crypto::RSAPrivateKey* private_key,
                                 const std::vector<uint8>& signature,
                                 const FilePath& crx_path) {
   if (file_util::PathExists(crx_path))
     file_util::Delete(crx_path, false);
   ScopedStdioHandle crx_handle(file_util::OpenFile(crx_path, "wb"));
+  if (!crx_handle.get()) {
+    error_message_ = l10n_util::GetStringUTF8(IDS_EXTENSION_SHARING_VIOLATION);
+    return false;
+  }
 
   std::vector<uint8> public_key;
   if (!private_key->ExportPublicKey(&public_key)) {
     error_message_ =
         l10n_util::GetStringUTF8(IDS_EXTENSION_PUBLIC_KEY_FAILED_TO_EXPORT);
     return false;
   }
 
   SandboxedExtensionUnpacker::ExtensionHeader header;
   memcpy(&header.magic, SandboxedExtensionUnpacker::kExtensionHeaderMagic,
@@ skipping 59 matching lines @@
   bool result = false;
   if (CreateZip(extension_dir, temp_dir.path(), &zip_path) &&
       SignZip(zip_path, key_pair.get(), &signature) &&
       WriteCRX(zip_path, key_pair.get(), signature, crx_path)) {
     result = true;
   }
 
   file_util::Delete(zip_path, false);
   return result;
 }