Revert of base: Remove using:: declaration from version.h header.

extensions/common/extension.cc

 // Copyright (c) 2013 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 "extensions/common/extension.h"
 
 #include "base/base64.h"
 #include "base/basictypes.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 558 matching lines @@
   name_ = base::UTF16ToUTF8(localized_name);
   return true;
 }
 
 bool Extension::LoadVersion(base::string16* error) {
   std::string version_str;
   if (!manifest_->GetString(keys::kVersion, &version_str)) {
     *error = base::ASCIIToUTF16(errors::kInvalidVersion);
     return false;
   }
-  version_.reset(new base::Version(version_str));
+  version_.reset(new Version(version_str));
   if (!version_->IsValid() || version_->components().size() > 4) {
     *error = base::ASCIIToUTF16(errors::kInvalidVersion);
     return false;
   }
   if (manifest_->HasKey(keys::kVersionName)) {
     if (!manifest_->GetString(keys::kVersionName, &version_name_)) {
       *error = base::ASCIIToUTF16(errors::kInvalidVersionName);
       return false;
     }
   }
@@ skipping 191 matching lines @@
 
 UpdatedExtensionPermissionsInfo::UpdatedExtensionPermissionsInfo(
     const Extension* extension,
     const PermissionSet* permissions,
     Reason reason)
     : reason(reason),
       extension(extension),
       permissions(permissions) {}
 
 }   // namespace extensions