Revert of Add ExtensionsApiClient interface, use it in the storage API SettingsFrontend

extensions/browser/api/extensions_api_client.h

-// 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.
-
-#ifndef EXTENSIONS_BROWSER_API_EXTENSIONS_API_CLIENT_H_
-#define EXTENSIONS_BROWSER_API_EXTENSIONS_API_CLIENT_H_
-
-#include <map>
-
-#include "base/memory/ref_counted.h"
-#include "extensions/browser/api/storage/settings_namespace.h"
-
-template <class T>
-class ObserverListThreadSafe;
-
-namespace content {
-class BrowserContext;
-}
-
-namespace extensions {
-
-class SettingsObserver;
-class SettingsStorageFactory;
-class ValueStoreCache;
-
-// Allows the embedder of the extensions module to customize its support for
-// API features. The embedder must create a single instance in the browser
-// process. Provides a default implementation that does nothing.
-class ExtensionsAPIClient {
- public:
-  // Construction sets the single instance.
-  ExtensionsAPIClient();
-
-  // Destruction clears the single instance.
-  virtual ~ExtensionsAPIClient();
-
-  // Returns the single instance of |this|.
-  static ExtensionsAPIClient* Get();
-
-  // Storage API support.
-
-  // Add any additional value store caches (e.g. for chrome.storage.managed)
-  // to |caches|. By default adds nothing.
-  virtual void AddAdditionalValueStoreCaches(
-      content::BrowserContext* context,
-      const scoped_refptr<SettingsStorageFactory>& factory,
-      const scoped_refptr<ObserverListThreadSafe<SettingsObserver> >& observers,
-      std::map<settings_namespace::Namespace, ValueStoreCache*>* caches);
-
-  // NOTE: If this interface gains too many methods (perhaps more than 20) it
-  // should be split into one interface per API.
-};
-
-}  // namespace extensions
-
-#endif  // EXTENSIONS_BROWSER_API_EXTENSIONS_API_CLIENT_H_