Move JoinString to the base namespace

chrome/browser/ui/libgtk2ui/select_file_dialog_impl_gtk2.cc

Index: chrome/browser/ui/libgtk2ui/select_file_dialog_impl_gtk2.cc
diff --git a/chrome/browser/ui/libgtk2ui/select_file_dialog_impl_gtk2.cc b/chrome/browser/ui/libgtk2ui/select_file_dialog_impl_gtk2.cc
index f9c8b53c89113cc51bcedcca340b967650670e0f..638407e3bc1b8c638b76725470872631aa98fd3a 100644
--- a/chrome/browser/ui/libgtk2ui/select_file_dialog_impl_gtk2.cc
+++ b/chrome/browser/ui/libgtk2ui/select_file_dialog_impl_gtk2.cc
@@ -319,7 +319,8 @@ void SelectFileDialogImplGTK::AddFilters(GtkFileChooser* chooser) {
       // the extensions themselves if the description is blank.
       std::vector<std::string> fallback_labels_vector(fallback_labels.begin(),
                                                       fallback_labels.end());
-      std::string fallback_label = JoinString(fallback_labels_vector, ',');
+      std::string fallback_label =
+          base::JoinString(fallback_labels_vector, ",");
       gtk_file_filter_set_name(filter, fallback_label.c_str());
     }