PlzNavigate: Refactor unit test helper functions

content/test/test_navigation_url_loader_factory.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 "content/test/test_navigation_url_loader_factory.h"
+
+#include "content/browser/loader/navigation_url_loader.h"
+#include "content/test/test_navigation_url_loader.h"
+
+namespace content {
+
+TestNavigationURLLoaderFactory::TestNavigationURLLoaderFactory() {
+  NavigationURLLoader::SetFactoryForTesting(this);

[carlosk, 2014/11/17 10:46:56]

Should we add a DCHECK in the implementation of SetFactoryForTesting to confirm
there isn't a factory already set?

[clamy, 2014/11/18 12:33:22]

Done.

+}
+
+TestNavigationURLLoaderFactory::~TestNavigationURLLoaderFactory() {
+  NavigationURLLoader::SetFactoryForTesting(NULL);
+}
+
+scoped_ptr<NavigationURLLoader> TestNavigationURLLoaderFactory::CreateLoader(
+    BrowserContext* browser_context,
+    int64 frame_tree_node_id,
+    const CommonNavigationParams& common_params,
+    scoped_ptr<NavigationRequestInfo> request_info,
+    ResourceRequestBody* request_body,
+    NavigationURLLoaderDelegate* delegate) {
+  return scoped_ptr<NavigationURLLoader>(new TestNavigationURLLoader(
+      common_params, request_info.Pass(), delegate));
+}
+
+}  // namespace content