Add base:: to string16s in win8/.

win8/test/open_with_dialog_async.h

Index: win8/test/open_with_dialog_async.h
diff --git a/win8/test/open_with_dialog_async.h b/win8/test/open_with_dialog_async.h
index 9f926454b0fa0089d6ac2e55a59d716cdfe6227f..62ddbed01ce1044b8aa538af7c5849eaf5a06967 100644
--- a/win8/test/open_with_dialog_async.h
+++ b/win8/test/open_with_dialog_async.h
@@ -25,8 +25,8 @@ typedef base::Callback<void(HRESULT)> OpenWithDialogCallback;
 // the dedicated thread will be leaked if the calling thread's message loop goes
 // away before the interaction completes.
 void OpenWithDialogAsync(HWND parent_window,
-                         const string16& file_name,
-                         const string16& file_type_class,
+                         const base::string16& file_name,
+                         const base::string16& file_type_class,
                          int open_as_info_flags,
                          const OpenWithDialogCallback& callback);