Add FakeClipboard implementation for unit 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/config/ui.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
@@ skipping 638 matching lines @@
   if (is_android || is_ios) {
     sources -= [
       "device_form_factor_desktop.cc",
     ]
   }
 }
 
 source_set("test_support") {
   testonly = true
   sources = [
+    "test/test_clipboard.cc",
+    "test/test_clipboard.h",
     "test/ui_controls.h",
     "test/ui_controls_aura.cc",
     "test/ui_controls_internal_win.cc",
     "test/ui_controls_internal_win.h",
     "test/ui_controls_mac.mm",
     "test/ui_controls_win.cc",
   ]
 
   public_deps = [
     ":base",
@@ skipping 52 matching lines @@
   sources = [
     "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",
     "models/tree_node_iterator_unittest.cc",
     "resource/data_pack_literal.cc",
     "resource/data_pack_unittest.cc",
     "resource/resource_bundle_unittest.cc",
+    "test/test_clipboard_unittest.cc",
     "test/run_all_unittests.cc",
   ]
 
   if (is_ios) {
     # Compile this Mac file on iOS as well.
     set_sources_assignment_filter([])
     sources += [ "l10n/l10n_util_mac_unittest.mm" ]
     set_sources_assignment_filter(sources_assignment_filter)
   } else {  # !is_ios
     sources += [
@@ skipping 175 matching lines @@
       "//ui/chromeos:ui_chromeos",
       "//ui/events:gesture_detection",
       "//ui/message_center:message_center",
       "//ui/views",
       "//ui/views:test_support",
     ]
   }
 }
 }
 # TODO(GYP) Mac (ui_unittest_bundle) and Android (ui_unittests_apk).