Add xdg mime support on Linux.

net/base/platform_mime_util_linux.cc

 // Copyright (c) 2006-2008 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.
 
 #include <string>
 
+#include "base/logging.h"
+#include "base/mime_util.h"
 #include "net/base/platform_mime_util.h"
 
 namespace net {
 
 bool PlatformMimeUtil::GetPlatformMimeTypeFromExtension(
     const FilePath::StringType& ext, std::string* result) const {
-  // The correct thing to do is to interact somehow with the freedesktop shared
-  // mime info cache. Since Linux (and other traditional *IX systems) don't use
-  // file extensions; they use mime types and have multiple ways of detecting
-  // that; some types can be guessed from globs (*.gif), but there's a whole
-  // bunch that use a magic byte test.
-  //
-  // Since this method only is called from inside mime_util where there is
-  // already a hard coded table of mime types, we just return false because it
-  // doesn't matter.
-
-  return false;
+  FilePath::StringType dummy_path = "foo." + ext;
+  std::string out = mime_util::GetFileMimeType(dummy_path);
+  // GetFileMimeType likes to return application/octet-stream
+  // for everything it doesn't know - ignore that.
+  if (out == "application/octet-stream" || !out.length())
+    return false;
+  *result = out;
+  return true;
 }
 
 bool PlatformMimeUtil::GetPreferredExtensionForMimeType(
     const std::string& mime_type, FilePath::StringType* ext) const {
   // Unlike GetPlatformMimeTypeFromExtension, this method doesn't have a
   // default list that it uses, but for now we are also returning false since
   // this doesn't really matter as much under Linux.
   //
   // If we wanted to do this properly, we would read the mime.cache file which
   // has a section where they assign a glob (*.gif) to a mimetype
   // (image/gif). We look up the "heaviest" glob for a certain mime type and
   // then then try to chop off "*.".
 
+  NOTIMPLEMENTED();
   return false;
 }
 
 }  // namespace net