Move some more file utils to the base namespace.

base/nix/xdg_util.cc

Index: base/nix/xdg_util.cc
diff --git a/base/nix/xdg_util.cc b/base/nix/xdg_util.cc
index b3caf2abe0b020d32aa67917bc1a2fc3f6d57433..4c1510f5c116acf0e0276b87c3217cbb5c59370a 100644
--- a/base/nix/xdg_util.cc
+++ b/base/nix/xdg_util.cc
@@ -31,7 +31,7 @@ FilePath GetXDGDirectory(Environment* env, const char* env_name,
   if (env->GetVar(env_name, &env_value) && !env_value.empty())
     path = FilePath(env_value);
   else
-    path = file_util::GetHomeDir().Append(fallback_dir);
+    path = GetHomeDir().Append(fallback_dir);
   return path.StripTrailingSeparators();
 }
 
@@ -42,7 +42,7 @@ FilePath GetXDGUserDirectory(const char* dir_name, const char* fallback_dir) {
     path = FilePath(xdg_dir);
     free(xdg_dir);
   } else {
-    path = file_util::GetHomeDir().Append(fallback_dir);
+    path = GetHomeDir().Append(fallback_dir);
   }
   return path.StripTrailingSeparators();
 }