linux: prompt before overwriting a file in downloads

chrome/browser/gtk/dialogs_gtk.cc

 // Copyright (c) 2009 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 <gtk/gtk.h>
 #include <map>
 #include <set>
 
 #include "app/l10n_util.h"
 #include "base/file_util.h"
@@ skipping 420 matching lines @@
     // recommendation of the GTK docs.
     gtk_file_chooser_set_current_folder(GTK_FILE_CHOOSER(dialog),
         default_path.DirName().value().c_str());
     gtk_file_chooser_set_current_name(GTK_FILE_CHOOSER(dialog),
         default_path.BaseName().value().c_str());
   } else if (!last_saved_path_->empty()) {
     gtk_file_chooser_set_current_folder(GTK_FILE_CHOOSER(dialog),
                                         last_saved_path_->value().c_str());
   }
   gtk_file_chooser_set_select_multiple(GTK_FILE_CHOOSER(dialog), FALSE);
+  gtk_file_chooser_set_do_overwrite_confirmation(GTK_FILE_CHOOSER(dialog),
+                                                 TRUE);
   g_signal_connect(G_OBJECT(dialog), "response",
                    G_CALLBACK(OnSelectSingleFileDialogResponse), this);
   return dialog;
 }
 
 void* SelectFileDialogImpl::PopParamsForDialog(GtkWidget* dialog) {
   std::map<GtkWidget*, void*>::iterator iter = params_map_.find(dialog);
   DCHECK(iter != params_map_.end());
   void* params = iter->second;
   params_map_.erase(iter);
@@ skipping 123 matching lines @@
   // This will preserve the image's aspect ratio.
   GdkPixbuf* pixbuf = gdk_pixbuf_new_from_file_at_size(filename, kPreviewWidth,
                                                        kPreviewHeight, NULL);
   g_free(filename);
   if (pixbuf) {
     gtk_image_set_from_pixbuf(GTK_IMAGE(dialog->preview_), pixbuf);
     g_object_unref(pixbuf);
   }
   gtk_file_chooser_set_preview_widget_active(chooser, pixbuf ? TRUE : FALSE);
 }