Move PathIsWritable, DirectoryExists, ContentsEqual, and TextContentsEqual to the base namespace.

ui/shell_dialogs/select_file_dialog_mac.mm

Index: ui/shell_dialogs/select_file_dialog_mac.mm
diff --git a/ui/shell_dialogs/select_file_dialog_mac.mm b/ui/shell_dialogs/select_file_dialog_mac.mm
index 15113184ca7b425b878a3c0c726690fc92b11ac3..218d39dc90970f0cc89de5e5038dfc5698a98a5a 100644
--- a/ui/shell_dialogs/select_file_dialog_mac.mm
+++ b/ui/shell_dialogs/select_file_dialog_mac.mm
@@ -200,7 +200,7 @@ void SelectFileDialogImpl::SelectFileImpl(
     // The file dialog is going to do a ton of stats anyway. Not much
     // point in eliminating this one.
     base::ThreadRestrictions::ScopedAllowIO allow_io;
-    if (file_util::DirectoryExists(default_path)) {
+    if (base::DirectoryExists(default_path)) {
       default_dir = base::SysUTF8ToNSString(default_path.value());
     } else {
       default_dir = base::SysUTF8ToNSString(default_path.DirName().value());