Clean up and simplify how we deal with filename extensions on Windows. Allow...

chrome/browser/shell_dialogs.h

Index: chrome/browser/shell_dialogs.h
===================================================================
--- chrome/browser/shell_dialogs.h	(revision 51758)
+++ chrome/browser/shell_dialogs.h	(working copy)
@@ -17,6 +17,12 @@
 class Font;
 }
 
+// This function is declared extern such that it is accessible for unit tests
+// in /chrome/browser/views/shell_dialogs_win_unittest.cc
+extern std::wstring AppendExtensionIfNeeded(const std::wstring& filename,
+                                            const std::wstring& filter_selected,
+                                            const std::wstring& suggested_ext);
+
 // A base class for shell dialogs.
 class BaseShellDialog {
  public: