Dismiss action in tab modal dialogs.

ui/views/window/dialog_delegate.cc

Index: ui/views/window/dialog_delegate.cc
diff --git a/ui/views/window/dialog_delegate.cc b/ui/views/window/dialog_delegate.cc
index f99a3dd8135c7efb87c6dfb4fdde2bbbf52b096f..c23cd6cb9a0af689195e536201be5a9a4386a2ce 100644
--- a/ui/views/window/dialog_delegate.cc
+++ b/ui/views/window/dialog_delegate.cc
@@ -83,6 +83,15 @@ bool DialogDelegate::Accept() {
   return true;
 }
 
+bool DialogDelegate::Dismiss() {
+  int buttons = GetDialogButtons();
+  if ((buttons & ui::DIALOG_BUTTON_CANCEL) ||
+      (buttons == ui::DIALOG_BUTTON_NONE)) {
+    return Cancel();
+  }
+  return Accept(true);
+}
+
 base::string16 DialogDelegate::GetDialogLabel() const {
   return base::string16();
 }