linux: Both gtk and the aura port should set the icon theme name.

base/nix/mime_util_xdg.h

 // Copyright (c) 2011 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_NIX_MIME_UTIL_XDG_H_
 #define BASE_NIX_MIME_UTIL_XDG_H_
 
 #include <string>
 
 #include "base/base_export.h"
 #include "build/build_config.h"
 
 namespace base {
 
 class FilePath;
 
 namespace nix {
 
 // 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.
 BASE_EXPORT std::string GetFileMimeType(const FilePath& filepath);
 
 // Get the mime type for a byte vector.
 BASE_EXPORT std::string GetDataMimeType(const std::string& data);
 
-#if defined(TOOLKIT_GTK)
-// This detects the current GTK theme by calling gtk_settings_get_default().
-// It should only be executed on the UI thread and must be called before
-// GetMimeIcon().
-BASE_EXPORT void DetectGtkTheme();
-#endif
+// Sets the current icon theme that we've detected from the desktop
+// environment. Currently only works when we believe we're in a GTK
+// environment.
+BASE_EXPORT void SetIconThemeName(const std::string& name);
 
 // 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.
 BASE_EXPORT FilePath GetMimeIcon(const std::string& mime_type, size_t size);
 
 }  // namespace nix
 }  // namespace base
 
 #endif  // BASE_NIX_MIME_UTIL_XDG_H_