Add new NSPasteboard utility function and tests.

ui/base/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/buildflag_header.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
@@ skipping 48 matching lines @@
     "accelerators/platform_accelerator.h",
     "accelerators/platform_accelerator_cocoa.h",
     "accelerators/platform_accelerator_cocoa.mm",
     "android/ui_base_jni_registrar.cc",
     "android/ui_base_jni_registrar.h",
     "clipboard/clipboard_android.cc",
     "clipboard/clipboard_android.h",
     "clipboard/clipboard_mac.h",
     "clipboard/clipboard_mac.mm",
     "clipboard/clipboard_types.h",
+    "clipboard/clipboard_util_mac.h",
+    "clipboard/clipboard_util_mac.mm",
     "clipboard/clipboard_util_win.cc",
     "clipboard/clipboard_util_win.h",
     "clipboard/clipboard_win.cc",
     "clipboard/clipboard_win.h",
     "clipboard/custom_data_helper_linux.cc",
     "clipboard/custom_data_helper_mac.mm",
     "cocoa/animation_utils.h",
     "cocoa/appkit_utils.h",
     "cocoa/appkit_utils.mm",
     "cocoa/base_view.h",
@@ skipping 629 matching lines @@
   ]
   outputs = [
     "{{bundle_resources_dir}}/" +
         "{{source_root_relative_dir}}/{{source_file_part}}",
   ]
 }
 
 # GYP version: ui/base/ui_base_tests.gyp:ui_base_unittests
 test("ui_base_unittests") {
   sources = [
+    "clipboard/clipboard_util_mac_unittest.mm",
     "ios/cru_context_menu_controller_unittest.mm",
     "l10n/l10n_util_mac_unittest.mm",
     "l10n/l10n_util_unittest.cc",
     "l10n/l10n_util_win_unittest.cc",
     "l10n/time_format_unittest.cc",
     "layout_unittest.cc",
     "material_design/material_design_controller_unittest.cc",
     "models/tree_node_iterator_unittest.cc",
     "resource/data_pack_literal.cc",
     "resource/data_pack_unittest.cc",
@@ skipping 209 matching lines @@
   }
   if (is_mac) {
     data += [ "$root_out_dir/ui_unittests Framework.framework/" ]
 
     if (is_asan && symbol_level == 0) {
       data += [ "$root_out_dir/ui_base_unittests.dSYM/" ]
     }
   }
 }
 # TODO(GYP) Mac (ui_base_tests_bundle)