### Problem Description
I use ubuntu linux. my system language is Chinese, but the dialog button labels is English by default. I found the buttonLabel option from the API to set the label of the save or open button, but the label of the cancel button is not supported.

### Proposed Solution
Support customizing cancel button label in Open and Save dialogs

shell/browser/ui/file_dialog_gtk.cc
gtk_widget_hide(dialog_);
  if (save_promise_) {
    mate::Dictionary dict =
        mate::Dictionary::CreateEmpty(save_promise_->isolate());
    if (response == GTK_RESPONSE_ACCEPT) {
      dict.Set("canceled", false);
      dict.Set("filePath", GetFileName());
    } else {
      dict.Set("canceled", true);
      dict.Set("filePath", base::FilePath());
    }
    save_promise_->Resolve(dict.GetHandle());
  } else if (open_promise_) {
    mate::Dictionary dict =
        mate::Dictionary::CreateEmpty(open_promise_->isolate());
    if (response == GTK_RESPONSE_ACCEPT) {
      dict.Set("canceled", false);
      dict.Set("filePaths", GetFileNames());
    } else {
      dict.Set("canceled", true);
      dict.Set("filePaths", std::vector<base::FilePath>());
    }
    open_promise_->Resolve(dict.GetHandle());
  }
  delete this;
}
void FileChooserDialog::AddFilters(const Filters& filters) {