Don't set a default action for ToolbarActionsBarBubbles.

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

Index: chrome/browser/ui/views/toolbar/toolbar_actions_bar_bubble_views.cc
diff --git a/chrome/browser/ui/views/toolbar/toolbar_actions_bar_bubble_views.cc b/chrome/browser/ui/views/toolbar/toolbar_actions_bar_bubble_views.cc
index a5530f685d9a8b8aab8b0a09e9e4b261498fac42..722739c44fcc92aad6d3a98e7219a340582cd0a0 100644
--- a/chrome/browser/ui/views/toolbar/toolbar_actions_bar_bubble_views.cc
+++ b/chrome/browser/ui/views/toolbar/toolbar_actions_bar_bubble_views.cc
@@ -102,6 +102,10 @@ int ToolbarActionsBarBubbleViews::GetDialogButtons() const {
   return buttons;
 }
 
+int ToolbarActionsBarBubbleViews::GetDefaultDialogButton() const {
+  return ui::DIALOG_BUTTON_NONE;

[Peter Kasting, 2016/06/17 19:14:41]

Nit: May want a relevant TODO here

+}
+
 base::string16 ToolbarActionsBarBubbleViews::GetDialogButtonLabel(
     ui::DialogButton button) const {
   return button == ui::DIALOG_BUTTON_OK ? delegate_->GetActionButtonText()