Consistently use namespaced base::Version in extensions code.

extensions/browser/user_script_loader.cc

Index: extensions/browser/user_script_loader.cc
diff --git a/extensions/browser/user_script_loader.cc b/extensions/browser/user_script_loader.cc
index f045bcf5c4459a35006ac32c1c55735b961e7396..43b41baeb8b96b3fda7a36f60ceaab7b3bab7f3c 100644
--- a/extensions/browser/user_script_loader.cc
+++ b/extensions/browser/user_script_loader.cc
@@ -115,7 +115,7 @@ bool UserScriptLoader::ParseMetadataHeader(const base::StringPiece& script_text,
       } else if (GetDeclarationValue(line, kNameDeclaration, &value)) {
         script->set_name(value);
       } else if (GetDeclarationValue(line, kVersionDeclaration, &value)) {
-        Version version(value);
+        base::Version version(value);
         if (version.IsValid())
           script->set_version(version.GetString());
       } else if (GetDeclarationValue(line, kDescriptionDeclaration, &value)) {