Add xdg mime support on Linux.

base/mime_util.h

Index: base/mime_util.h
===================================================================
--- base/mime_util.h	(revision 0)
+++ base/mime_util.h	(revision 0)
@@ -0,0 +1,28 @@
+// Copyright (c) 2009 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 BASE_MIME_UTIL_H_
+#define BASE_MIME_UTIL_H_
+
+#include <string>
+
+class FilePath;
+
+namespace mime_util {
+
+// Gets the mime type for a file based on its filename. The file path does not
+// have to exist. Please note because it doesn't touch the disk, this does not
+// work for directories.
+// If the mime type is unknown, this will return application/octet-stream.
+std::string GetFileMimeType(const std::string& file_path);
+
+// Gets the file name for an icon given the mime type and icon pixel size.
+// Where an icon is a square image of |size| x |size|.
+// This will try to find the closest matching icon. If that's not available,
+// then a generic icon, and finally an empty FilePath if all else fails.
+FilePath GetMimeIcon(const std::string& mime_type, size_t size);
+
+}  // namespace mime_util
+
+#endif  // BASE_MIME_UTIL_H_