Refactor ExtensionManifestTest to allow usage in src/extensions

chrome/common/extensions/manifest_tests/chrome_manifest_test.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 "chrome/common/extensions/manifest_tests/chrome_manifest_test.h"
+
+#include "base/files/file_path.h"
+#include "base/path_service.h"
+#include "chrome/common/chrome_paths.h"
+
+ChromeManifestTest::ChromeManifestTest() {
+}
+
+ChromeManifestTest::~ChromeManifestTest() {
+}
+
+base::FilePath ChromeManifestTest::GetTestDataDir() {
+  base::FilePath path;
+  PathService::Get(chrome::DIR_TEST_DATA, &path);
+  return path.AppendASCII("extensions").AppendASCII("manifest_tests");
+}