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

chrome/browser/extensions/unpacked_installer.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 "chrome/browser/extensions/unpacked_installer.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_util.h"
 #include "base/strings/string_util.h"
@@ skipping 196 matching lines @@
     if (!service || service->browser_terminating())
       return;
 
     // TODO(crbug.com/420147): Move this code to a utility class to avoid
     // duplication of SharedModuleService::CheckImports code.
     if (SharedModuleInfo::ImportsModules(extension())) {
       const std::vector<SharedModuleInfo::ImportInfo>& imports =
           SharedModuleInfo::GetImports(extension());
       std::vector<SharedModuleInfo::ImportInfo>::const_iterator i;
       for (i = imports.begin(); i != imports.end(); ++i) {
-        base::Version version_required(i->minimum_version);
+        Version version_required(i->minimum_version);
         const Extension* imported_module =
             service->GetExtensionById(i->extension_id, true);
         if (!imported_module) {
           ReportExtensionLoadError(kImportMissing);
           return;
         } else if (imported_module &&
                    !SharedModuleInfo::IsSharedModule(imported_module)) {
           ReportExtensionLoadError(kImportNotSharedModule);
           return;
         } else if (imported_module && (version_required.IsValid() &&
@@ skipping 141 matching lines @@
   service_weak_->OnExtensionInstalled(
       extension(), syncer::StringOrdinal(), kInstallFlagInstallImmediately);
 
   if (!callback_.is_null()) {
     callback_.Run(extension(), extension_path_, std::string());
     callback_.Reset();
   }
 }
 
 }  // namespace extensions