Introduce ThreadableLoadingContext: make threaded loading code one step away from Document

third_party/WebKit/Source/core/loader/LoadingContext.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/loader/LoadingContext.h"
+
+#include "core/dom/Document.h"
+#include "core/dom/TaskRunnerHelper.h"
+#include "platform/loader/fetch/ResourceFetcher.h"
+
+namespace blink {
+
+class DocumentLoadingContext : public LoadingContext {
+ public:
+  explicit DocumentLoadingContext(Document& document) : m_document(&document) {}
+
+  ~DocumentLoadingContext() override = default;
+
+  bool isContextThread() const override {
+    return m_document->isContextThread();
+  }
+
+  ResourceFetcher* getResourceFetcher() override {
+    DCHECK(isContextThread());
+    return m_document->fetcher();
+  }
+
+  SecurityOrigin* getSecurityOrigin() override {
+    DCHECK(isContextThread());
+    return m_document->getSecurityOrigin();
+  }
+
+  bool isSecureContext() const override {
+    DCHECK(isContextThread());
+    return m_document->isSecureContext();
+  }
+
+  KURL firstPartyForCookies() const override {
+    DCHECK(isContextThread());
+    return m_document->firstPartyForCookies();
+  }
+
+  String userAgent() const override {
+    DCHECK(isContextThread());
+    return m_document->userAgent();
+  }
+
+  Document* getLoadingDocument() override {
+    DCHECK(isContextThread());
+    return m_document.get();
+  }
+
+  RefPtr<WebTaskRunner> getTaskRunner(TaskType type) override {
+    return TaskRunnerHelper::get(type, m_document.get());
+  }
+
+  void recordUseCount(UseCounter::Feature feature) override {
+    UseCounter::count(m_document.get(), feature);
+  }
+
+  DEFINE_INLINE_VIRTUAL_TRACE() {
+    visitor->trace(m_document);
+    LoadingContext::trace(visitor);
+  }
+
+ private:
+  Member<Document> m_document;
+};
+
+LoadingContext* LoadingContext::create(Document& document) {
+  // For now this is the only default implementation.
+  return new DocumentLoadingContext(document);
+}
+
+}  // namespace blink