mac: use NSUserDefaults values for caret blink rate if present

ui/base/cocoa/defaults_utils.h

+// 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.
+
+#ifndef UI_BASE_COCOA_DEFAULTS_UTILS_H_
+#define UI_BASE_COCOA_DEFAULTS_UTILS_H_
+
+#include "base/time/time.h"
+#include "ui/base/ui_base_export.h"
+
+namespace ui {
+
+// Returns the text insertion caret blink period, if one is configured in
+// NSUserDefaults.
+UI_BASE_EXPORT bool TextInsertionCaretBlinkPeriod(base::TimeDelta* period);
+
+}
+
+#endif