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

chrome/common/extensions/manifest_handlers/minimum_chrome_version_checker.cc

Index: chrome/common/extensions/manifest_handlers/minimum_chrome_version_checker.cc
diff --git a/chrome/common/extensions/manifest_handlers/minimum_chrome_version_checker.cc b/chrome/common/extensions/manifest_handlers/minimum_chrome_version_checker.cc
index bedbf960c7e786bcf1a87ef262dbdbac891ea813..0bcc65e60d1723c70cd537c07bd9ddc994d55d2b 100644
--- a/chrome/common/extensions/manifest_handlers/minimum_chrome_version_checker.cc
+++ b/chrome/common/extensions/manifest_handlers/minimum_chrome_version_checker.cc
@@ -33,13 +33,13 @@ bool MinimumChromeVersionChecker::Parse(Extension* extension,
     return false;
   }
 
-  Version minimum_version(minimum_version_string);
+  base::Version minimum_version(minimum_version_string);
   if (!minimum_version.IsValid()) {
     *error = base::ASCIIToUTF16(errors::kInvalidMinimumChromeVersion);
     return false;
   }
 
-  Version current_version(version_info::GetVersionNumber());
+  base::Version current_version(version_info::GetVersionNumber());
   if (!current_version.IsValid()) {
     NOTREACHED();
     return false;