Extract DeclarativeUserScriptManager from ExtensionSystem.

extensions/browser/declarative_user_script_manager_factory.h

Index: extensions/browser/declarative_user_script_manager_factory.h
diff --git a/extensions/browser/declarative_user_script_manager_factory.h b/extensions/browser/declarative_user_script_manager_factory.h
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+++ b/extensions/browser/declarative_user_script_manager_factory.h
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+// Copyright 2015 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.
+
+#ifndef EXTENSIONS_BROWSER_DECLARATIVE_USER_SCRIPT_MANAGER_FACTORY_H_
+#define EXTENSIONS_BROWSER_DECLARATIVE_USER_SCRIPT_MANAGER_FACTORY_H_
+
+#include "base/memory/singleton.h"
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+
+namespace extensions {
+
+class DeclarativeUserScriptManager;
+
+class DeclarativeUserScriptManagerFactory
+    : public BrowserContextKeyedServiceFactory {
+ public:
+  static DeclarativeUserScriptManager* GetForBrowserContext(
+      content::BrowserContext* context);
+  static DeclarativeUserScriptManagerFactory* GetInstance();
+
+ private:
+  friend struct DefaultSingletonTraits<DeclarativeUserScriptManagerFactory>;
+
+  DeclarativeUserScriptManagerFactory();
+  ~DeclarativeUserScriptManagerFactory() override;
+
+  // BrowserContextKeyedServiceFactory implementation
+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(DeclarativeUserScriptManagerFactory);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_DECLARATIVE_USER_SCRIPT_MANAGER_FACTORY_H_