Do not record startup metrics when non-browser UI was displayed

chrome/browser/ui/simple_message_box_internal.h

+// Copyright 2015 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.
+
+#ifndef CHROME_BROWSER_UI_SIMPLE_MESSAGE_BOX_INTERNAL_H_
+#define CHROME_BROWSER_UI_SIMPLE_MESSAGE_BOX_INTERNAL_H_
+
+namespace chrome {
+namespace internal {
+// If true: skips prompting a blocking message box in tests in situations where
+// such UI would freeze the test, but behaves as though such a box had come up
+// and the user had clicked "OK". Defaults to false.
+extern bool g_should_skip_message_box_for_test;
+}  // namespace internal
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_UI_SIMPLE_MESSAGE_BOX_INTERNAL_H_