Fixes saving files that don't have valid extensions.

chrome/common/win_util.h

Index: chrome/common/win_util.h
===================================================================
--- chrome/common/win_util.h	(revision 13948)
+++ chrome/common/win_util.h	(working copy)
@@ -146,6 +146,9 @@
 //   ext_desc: { "Text Document" }
 //   returned: "Text Document\0*.txt\0HTML Document\0.htm;.html\0"
 //             "All Files\0*.*\0\0" (in one big string)
+// If a description is not provided for a file extension, it will be retrieved
+// from the registry. If the file extension does not exist in the registry, it
+// will be omitted from the filter, as it is likely a bogus extension.
 std::wstring FormatFilterForExtensions(
     const std::vector<std::wstring>& file_ext,
     const std::vector<std::wstring>& ext_desc,