Introduced WebFactory and WebFactoryImpl for constructing web/ classes

third_party/WebKit/Source/core/exported/WebFactory.cpp

+// Copyright 2017 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 "core/exported/WebFactory.h"
+#include "platform/wtf/Assertions.h"
+
+namespace blink {
+
+WebFactory* WebFactory::factory_instance_ = nullptr;
+
+WebFactory& WebFactory::GetInstance() {
+  DCHECK(factory_instance_);
+  return *factory_instance_;
+}
+
+void WebFactory::SetInstance(WebFactory& factory) {
+  DCHECK_EQ(nullptr, factory_instance_);
+  factory_instance_ = &factory;
+}
+
+}  // namespace blink