Pressing "enter" while the JS prompt text entry has focus should

chrome/browser/app_modal_dialog_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 "chrome/browser/app_modal_dialog.h"
 
 #include <gtk/gtk.h>
 
 #include "app/l10n_util.h"
 #include "app/message_box_flags.h"
@@ skipping 86 matching lines @@
 
     default:
       NOTREACHED();
   }
 
   GtkWindow* window = tab_contents_->view()->GetTopLevelNativeWindow();
   dialog_ = gtk_message_dialog_new(window, GTK_DIALOG_MODAL,
       message_type, buttons, "%s", WideToUTF8(message_text_).c_str());
   gtk_window_set_title(GTK_WINDOW(dialog_), WideToUTF8(title_).c_str());
 
-  // Adjust content area as needed.
+  // Adjust content area as needed.  Set up the prompt text entry or
+  // suppression check box.
   if (MessageBoxFlags::kIsJavascriptPrompt == dialog_flags_) {
     // TODO(tc): Replace with gtk_dialog_get_content_area() when using GTK 2.14+
     GtkWidget* contents_vbox = GTK_DIALOG(dialog_)->vbox;
     GtkWidget* text_box = gtk_entry_new();
     gtk_entry_set_text(GTK_ENTRY(text_box),
                        WideToUTF8(default_prompt_text_).c_str());
     gtk_box_pack_start(GTK_BOX(contents_vbox), text_box, TRUE, TRUE, 0);
     g_object_set_data(G_OBJECT(dialog_), kPromptTextId, text_box);
+    gtk_entry_set_activates_default(GTK_ENTRY(text_box), TRUE);
   }
 
   if (display_suppress_checkbox_) {
     GtkWidget* contents_vbox = GTK_DIALOG(dialog_)->vbox;
     GtkWidget* check_box = gtk_check_button_new_with_label(
         l10n_util::GetStringUTF8(
             IDS_JAVASCRIPT_MESSAGEBOX_SUPPRESS_OPTION).c_str());
     gtk_box_pack_start(GTK_BOX(contents_vbox), check_box, TRUE, TRUE, 0);
     g_object_set_data(G_OBJECT(dialog_), kSuppressCheckboxId, check_box);
   }
@@ skipping 49 matching lines @@
   }
 }
 
 void AppModalDialog::AcceptWindow() {
   OnDialogResponse(GTK_DIALOG(dialog_), GTK_RESPONSE_OK, this);
 }
 
 void AppModalDialog::CancelWindow() {
   OnDialogResponse(GTK_DIALOG(dialog_), GTK_RESPONSE_CANCEL, this);
 }