Add FakeClipboard implementation for unit tests.

ui/base/test/test_clipboard_unittest.cc

+// 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.
+
+#include "ui/base/test/test_clipboard.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace ui {
+
+struct TestClipboardTraits {
+  static Clipboard* Create() {
+    TestClipboard::UseForCurrentThread();
+    return Clipboard::GetForCurrentThread();
+  }
+
+  static void Destroy(Clipboard* clipboard) {
+    ASSERT_EQ(Clipboard::GetForCurrentThread(), clipboard);
+    Clipboard::DestroyClipboardForCurrentThread();
+  }
+};
+
+typedef TestClipboardTraits TypesToTest;
+
+}  // namespace ui
+
+#include "ui/base/clipboard/clipboard_test_template.h"