Don't set a default action for ToolbarActionsBarBubbles.

chrome/browser/ui/views/toolbar/toolbar_actions_bar_bubble_views.cc

 // Copyright 2016 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/ui/views/toolbar/toolbar_actions_bar_bubble_views.h"
 
 #include "chrome/browser/ui/toolbar/toolbar_actions_bar_bubble_delegate.h"
 #include "chrome/browser/ui/view_ids.h"
 #include "chrome/grit/locale_settings.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 84 matching lines @@
   }
 }
 
 int ToolbarActionsBarBubbleViews::GetDialogButtons() const {
   int buttons = ui::DIALOG_BUTTON_OK;
   if (!delegate_->GetDismissButtonText().empty())
     buttons |= ui::DIALOG_BUTTON_CANCEL;
   return buttons;
 }
 
+int ToolbarActionsBarBubbleViews::GetDefaultDialogButton() const {
+  // TODO(estade): we should set a default where approprite. See
+  // http://crbug.com/621122
+  return ui::DIALOG_BUTTON_NONE;
+}
+
 base::string16 ToolbarActionsBarBubbleViews::GetDialogButtonLabel(
     ui::DialogButton button) const {
   return button == ui::DIALOG_BUTTON_OK ? delegate_->GetActionButtonText()
                                         : delegate_->GetDismissButtonText();
 }
 
 void ToolbarActionsBarBubbleViews::LinkClicked(views::Link* link,
                                                int event_flags) {
   delegate_->OnBubbleClosed(ToolbarActionsBarBubbleDelegate::CLOSE_LEARN_MORE);
   // Reset delegate so we don't send extra OnBubbleClosed()s.
   delegate_.reset();
   GetWidget()->Close();
 }