Clean up threading model of external extension providers

chrome/browser/extensions/external_extension_provider_impl.h

+// Copyright (c) 2011 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 CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_IMPL_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_IMPL_H_
+#pragma once
+
+#include "chrome/browser/extensions/external_extension_provider_interface.h"
+
+#include "base/ref_counted.h"
+#include "chrome/browser/extensions/external_extension_loader.h"
+
+class DictionaryValue;
+class ExternalExtensionLoader;
+class Profile;
+class ValueSerializer;
+class Version;
+
+// A specialization of the ExternalExtensionProvider that uses an instance
+// of ExternalExtensionLoader to provide external extensions. This class
+// can be seen as a bridge between the extension system and an
+// ExternalExtensionLoader. Instances live their entire life on the UI thread.
+class ExternalExtensionProviderImpl
+    : public ExternalExtensionProviderInterface {
+ public:
+  // The constructed provider will provide the extensions loaded from |loader|
+  // to |service|, that will deal with the installation. The location
+  // attributes of the provided extensions are also specified here:
+  // |crx_location|: extensions originating from crx files
+  // |download_location|: extensions originating from update URLs
+  // If either of the origins is not supported by this provider, then it should
+  // be initialized as Extensions::INVALID.
+  ExternalExtensionProviderImpl(
+      VisitorInterface* service,
+      ExternalExtensionLoader* loader,
+      Extension::Location crx_location,
+      Extension::Location download_location);
+
+  virtual ~ExternalExtensionProviderImpl();
+
+  // Populates a list with providers for all known sources.
+  static void CreateExternalProviders(
+      VisitorInterface* service,
+      Profile* profile,
+      ProviderCollection* provider_list);
+
+  // Sets underlying prefs and notifies provider. Only to be called by the
+  // owned ExternalExtensionLoader instance.
+  void SetPrefs(DictionaryValue* prefs);
+
+  // ExternalExtensionProvider implementation:
+  virtual void VisitRegisteredExtension() const;
+
+  virtual bool HasExtension(const std::string& id) const;
+
+  virtual bool GetExtensionDetails(const std::string& id,
+                                   Extension::Location* location,
+                                   scoped_ptr<Version>* version) const;
+
+  virtual void ServiceShutdown();
+
+  virtual bool IsReady();
+
+  static const char kLocation[];
+  static const char kState[];
+  static const char kExternalCrx[];
+  static const char kExternalVersion[];
+  static const char kExternalUpdateUrl[];
+
+ private:
+  // Location for external extensions that are provided by this provider from
+  // local crx files.
+  const Extension::Location crx_location_;
+
+  // Location for external extensions that are provided by this provider from
+  // update URLs.
+  const Extension::Location download_location_;
+
+ private:
+  // Weak pointer to the object that consumes the external extensions.
+  // This is zeroed out by: ServiceShutdown()
+  VisitorInterface* service_;  // weak
+
+  // Dictionary of the external extensions that are provided by this provider.
+  scoped_ptr<DictionaryValue> prefs_;
+
+  // Indicates that the extensions provided by this provider are loaded
+  // entirely.
+  bool ready_;
+
+  // The loader that loads the list of external extensions and reports them
+  // via |SetPrefs|.
+  scoped_refptr<ExternalExtensionLoader> loader_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExternalExtensionProviderImpl);
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_IMPL_H_