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

chrome/common/extensions/manifest_handlers/minimum_chrome_version_checker.cc

 // Copyright 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/common/extensions/manifest_handlers/minimum_chrome_version_checker.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "base/version.h"
 #include "chrome/grit/chromium_strings.h"
 #include "components/version_info/version_info.h"
@@ skipping 15 matching lines @@
 
 bool MinimumChromeVersionChecker::Parse(Extension* extension,
                                         base::string16* error) {
   std::string minimum_version_string;
   if (!extension->manifest()->GetString(keys::kMinimumChromeVersion,
                                         &minimum_version_string)) {
     *error = base::ASCIIToUTF16(errors::kInvalidMinimumChromeVersion);
     return false;
   }
 
-  base::Version minimum_version(minimum_version_string);
+  Version minimum_version(minimum_version_string);
   if (!minimum_version.IsValid()) {
     *error = base::ASCIIToUTF16(errors::kInvalidMinimumChromeVersion);
     return false;
   }
 
-  base::Version current_version(version_info::GetVersionNumber());
+  Version current_version(version_info::GetVersionNumber());
   if (!current_version.IsValid()) {
     NOTREACHED();
     return false;
   }
 
   if (current_version.CompareTo(minimum_version) < 0) {
     *error = ErrorUtils::FormatErrorMessageUTF16(
         errors::kChromeVersionTooLow,
         l10n_util::GetStringUTF8(IDS_PRODUCT_NAME),
         minimum_version_string);
     return false;
   }
   return true;
 }
 
 const std::vector<std::string> MinimumChromeVersionChecker::Keys() const {
   return SingleKey(keys::kMinimumChromeVersion);
 }
 
 }  // namespace extensions