Add KeyedServiceShutdownNotifier for classes that depend on keyed services but...

Add KeyedServiceShutdownNotifier for classes that depend on keyed services but can't be keyed services themselves.

BUG=395391

Review URL: https://codereview.chromium.org/905703002

Cr-Commit-Position: refs/heads/master@{#315234}

components/keyed_service.gypi

@@ -32,6 +32,8 @@
         'keyed_service/core/keyed_service_export.h',
         'keyed_service/core/keyed_service_factory.cc',
         'keyed_service/core/keyed_service_factory.h',
+        'keyed_service/core/keyed_service_shutdown_notifier.cc',
+        'keyed_service/core/keyed_service_shutdown_notifier.h',
         'keyed_service/core/refcounted_keyed_service.cc',
         'keyed_service/core/refcounted_keyed_service.h',
         'keyed_service/core/refcounted_keyed_service_factory.cc',
@@ -70,6 +72,8 @@
             'keyed_service/content/browser_context_keyed_base_factory.cc',
             'keyed_service/content/browser_context_keyed_service_factory.cc',
             'keyed_service/content/browser_context_keyed_service_factory.h',
+            'keyed_service/content/browser_context_keyed_service_shutdown_notifier_factory.cc',
+            'keyed_service/content/browser_context_keyed_service_shutdown_notifier_factory.h',
             'keyed_service/content/refcounted_browser_context_keyed_service_factory.cc',
             'keyed_service/content/refcounted_browser_context_keyed_service_factory.h',
         ],

components/keyed_service/content/BUILD.gn

@@ -13,6 +13,8 @@ component("content") {
     "browser_context_keyed_base_factory.cc",
     "browser_context_keyed_service_factory.cc",
     "browser_context_keyed_service_factory.h",
+    "browser_context_keyed_service_shutdown_notifier_factory.cc",
+    "browser_context_keyed_service_shutdown_notifier_factory.h",
     "refcounted_browser_context_keyed_service_factory.cc",
     "refcounted_browser_context_keyed_service_factory.h",
   ]

components/keyed_service/content/browser_context_keyed_service_shutdown_notifier_factory.cc

+// 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.
+
+#include "components/keyed_service/content/browser_context_keyed_service_shutdown_notifier_factory.h"
+
+#include "components/keyed_service/content/browser_context_dependency_manager.h"
+#include "components/keyed_service/core/keyed_service_shutdown_notifier.h"
+
+BrowserContextKeyedServiceShutdownNotifierFactory::
+    BrowserContextKeyedServiceShutdownNotifierFactory(const char* name)
+    : BrowserContextKeyedServiceFactory(
+          name,
+          BrowserContextDependencyManager::GetInstance()) {
+}
+BrowserContextKeyedServiceShutdownNotifierFactory::
+    ~BrowserContextKeyedServiceShutdownNotifierFactory() {
+}
+
+KeyedServiceShutdownNotifier*
+BrowserContextKeyedServiceShutdownNotifierFactory::Get(
+    content::BrowserContext* context) {
+  return static_cast<KeyedServiceShutdownNotifier*>(
+      GetServiceForBrowserContext(context, true));
+}
+
+KeyedService*
+BrowserContextKeyedServiceShutdownNotifierFactory::BuildServiceInstanceFor(
+    content::BrowserContext* context) const {
+  return new KeyedServiceShutdownNotifier;
+}
+
+content::BrowserContext*
+BrowserContextKeyedServiceShutdownNotifierFactory::GetBrowserContextToUse(
+    content::BrowserContext* context) const {
+  return context;
+}

components/keyed_service/content/browser_context_keyed_service_shutdown_notifier_factory.h

+// 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 COMPONENTS_KEYED_SERVICE_CONTENT_BROWSER_CONTEXT_KEYED_SERVICE_SHUTDOWN_NOTIFIER_FACTORY_H_
+#define COMPONENTS_KEYED_SERVICE_CONTENT_BROWSER_CONTEXT_KEYED_SERVICE_SHUTDOWN_NOTIFIER_FACTORY_H_
+
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+#include "components/keyed_service/core/keyed_service_export.h"
+
+class KeyedServiceShutdownNotifier;
+
+// A base class for factories for KeyedServiceShutdownNotifier objects that are
+// keyed on a BrowserContext.
+// To use this class, create a singleton subclass and declare its dependencies
+// in the constructor.
+class KEYED_SERVICE_EXPORT BrowserContextKeyedServiceShutdownNotifierFactory
+    : public BrowserContextKeyedServiceFactory {
+ public:
+  KeyedServiceShutdownNotifier* Get(content::BrowserContext* context);
+
+ protected:
+  explicit BrowserContextKeyedServiceShutdownNotifierFactory(const char* name);
+  ~BrowserContextKeyedServiceShutdownNotifierFactory() override;
+
+ private:
+  KeyedService* BuildServiceInstanceFor(
+      content::BrowserContext* context) const override;
+  content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const override;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserContextKeyedServiceShutdownNotifierFactory);
+};
+
+#endif  // COMPONENTS_KEYED_SERVICE_CONTENT_BROWSER_CONTEXT_KEYED_SERVICE_SHUTDOWN_NOTIFIER_FACTORY_H_

components/keyed_service/core/BUILD.gn

@@ -17,6 +17,8 @@ component("core") {
     "keyed_service_export.h",
     "keyed_service_factory.cc",
     "keyed_service_factory.h",
+    "keyed_service_shutdown_notifier.cc",
+    "keyed_service_shutdown_notifier.h",
     "refcounted_keyed_service.cc",
     "refcounted_keyed_service.h",
     "refcounted_keyed_service_factory.cc",

components/keyed_service/core/keyed_service_shutdown_notifier.cc

+// 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.
+
+#include "components/keyed_service/core/keyed_service_export.h"
+#include "components/keyed_service/core/keyed_service_shutdown_notifier.h"
+
+KeyedServiceShutdownNotifier::KeyedServiceShutdownNotifier() {
+}
+KeyedServiceShutdownNotifier::~KeyedServiceShutdownNotifier() {
+}
+
+scoped_ptr<base::CallbackList<void()>::Subscription>
+KeyedServiceShutdownNotifier::Subscribe(const base::Closure& callback) {
+  return callback_list_.Add(callback);
+}
+
+void KeyedServiceShutdownNotifier::Shutdown() {
+  callback_list_.Notify();
+}

components/keyed_service/core/keyed_service_shutdown_notifier.h

+// 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 COMPONENTS_KEYED_SERVICE_CORE_KEYED_SERVICE_SHUTDOWN_NOTIFIER_H_
+#define COMPONENTS_KEYED_SERVICE_CORE_KEYED_SERVICE_SHUTDOWN_NOTIFIER_H_
+
+#include "base/callback_list.h"
+#include "components/keyed_service/core/keyed_service.h"
+
+// This is a helper class for objects that depend on one or more keyed services,
+// but which cannot be keyed services themselves, for example because they don't
+// correspond 1:1 to a context, or because they have a different lifetime.
+//
+// To use this class, add a factory class and declare the dependencies there.
+// This class (being a KeyedService itself) will be shut down before its
+// dependencies and notify its observers.
+class KEYED_SERVICE_EXPORT KeyedServiceShutdownNotifier : public KeyedService {
+ public:
+  using Subscription = base::CallbackList<void()>::Subscription;
+
+  KeyedServiceShutdownNotifier();
+  ~KeyedServiceShutdownNotifier() override;
+
+  // Subscribe for a notification when the keyed services this object depends on
+  // (as defined by its factory) are shut down. The subscription object can be
+  // destroyed to unsubscribe.
+  scoped_ptr<Subscription> Subscribe(const base::Closure& callback);
+
+ private:
+  // KeyedService implementation:
+  void Shutdown() override;
+
+  base::CallbackList<void()> callback_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(KeyedServiceShutdownNotifier);
+};
+
+#endif  // COMPONENTS_KEYED_SERVICE_CORE_KEYED_SERVICE_SHUTDOWN_NOTIFIER_H_