Add new NSPasteboard utility function and tests.

ui/base/clipboard/clipboard_util_mac.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_CLIPBOARD_CLIPBOARD_UTIL_MAC_H_
+#define UI_BASE_CLIPBOARD_CLIPBOARD_UTIL_MAC_H_
+
+#import <AppKit/AppKit.h>
+
+#include "base/mac/scoped_nsobject.h"
+#include "ui/base/ui_base_export.h"
+
+namespace ui {
+
+class UI_BASE_EXPORT ClipboardUtil {
+ public:
+  // Returns an NSPasteboardItem that represents the given |url|.
+  // |url| must not be nil.
+  // If |title| is nil, |url| is used in its place.
+  static base::scoped_nsobject<NSPasteboardItem> PasteboardItemFromUrl(
+      NSString* url,
+      NSString* title);
+};
+}
+
+#endif  // UI_BASE_CLIPBOARD_CLIPBOARD_UTIL_MAC_H_