Introduce a helper for OPENFILENAME struct to make certain logic testable.

ui/base/win/open_file_name_win.h

+// Copyright (c) 2014 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.
+
+#ifndef UI_BASE_WIN_OPEN_FILE_NAME_WIN_H_
+#define UI_BASE_WIN_OPEN_FILE_NAME_WIN_H_
+
+#include <Windows.h>
+#include <Commdlg.h>
+
+#include <vector>
+
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "base/tuple.h"
+#include "ui/base/ui_base_export.h"
+
+namespace base {
+class FilePath;
+}  // namespace base
+
+namespace ui {
+namespace win {
+
+// Encapsulates an OPENFILENAME struct and related buffers. Also provides static
+// methods for interpreting the properties of an OPENFILENAME.
+class UI_BASE_EXPORT OpenFileName {
+ public:
+  // Initializes the OPENFILENAME, which may be accessed using Get(). All fields
+  // will be NULL except for |lStructSize|, |lpstrFile|, and |nMaxFile|. The
+  // file buffer will initially contain a null-terminated empty string.
+  OpenFileName(HWND parent_window, DWORD flags);
+  ~OpenFileName();
+
+  // Sets |lpstrInitialDir| and |lpstrFile|.
+  void SetInitialSelection(const base::FilePath& initial_directory,
+                           const base::FilePath& initial_filename);
+
+  // Returns the single selected file, or an empty path if there are more or
+  // less than one results.
+  base::FilePath GetSingleResult();
+
+  // Returns the selected file or files.
+  void GetResult(base::FilePath* directory,
+                 std::vector<base::FilePath>* filenames);
+
+  // Returns the OPENFILENAME structure.
+  OPENFILENAME* GetOPENFILENAME() { return &openfilename_; }
+
+ private:
+  OPENFILENAME openfilename_;
+  base::string16 initial_directory_buffer_;
+  wchar_t filename_buffer_[UNICODE_STRING_MAX_CHARS];
+
+  DISALLOW_COPY_AND_ASSIGN(OpenFileName);
+};
+
+}  // namespace win
+}  // namespace ui
+
+#endif  // UI_BASE_WIN_OPEN_FILE_NAME_WIN_H_