Add Observer to //ios/chrome's IdentityManagerFactory

IdentityManagerFactoryObserver is a parallel interface to //ios/chrome's
SigninManagerFactoryObserver. It will be used to replace usage of
that observer in follow up CLs.

BUG=927343

hange-Id: I5d32caf0fa0c24b692b6d5ccaf6f8d191818fd74
Change-Id: I801a883aa72ee69e3686fff58ddd4b5c893c799c
Reviewed-on: https://chromium-review.googlesource.com/c/1448473
Auto-Submit: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#628325}

ios/chrome/browser/signin/BUILD.gn

@@ -36,6 +36,7 @@ source_set("signin") {
     "gaia_cookie_manager_service_factory.h",
     "identity_manager_factory.cc",
     "identity_manager_factory.h",
+    "identity_manager_factory_observer.h",
     "identity_service_creator.cc",
     "identity_service_creator.h",
     "ios_chrome_signin_client.h",

ios/chrome/browser/signin/identity_manager_factory.cc

@@ -12,6 +12,7 @@
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/signin/account_tracker_service_factory.h"
 #include "ios/chrome/browser/signin/gaia_cookie_manager_service_factory.h"
+#include "ios/chrome/browser/signin/identity_manager_factory_observer.h"
 #include "ios/chrome/browser/signin/profile_oauth2_token_service_factory.h"
 #include "ios/chrome/browser/signin/signin_manager_factory.h"
 #include "services/identity/public/cpp/accounts_mutator.h"
@@ -75,8 +76,33 @@ IdentityManagerFactory* IdentityManagerFactory::GetInstance() {
   return instance.get();
 }
 
+void IdentityManagerFactory::AddObserver(
+    IdentityManagerFactoryObserver* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void IdentityManagerFactory::RemoveObserver(
+    IdentityManagerFactoryObserver* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
 std::unique_ptr<KeyedService> IdentityManagerFactory::BuildServiceInstanceFor(
     web::BrowserState* browser_state) const {
-  return std::make_unique<IdentityManagerWrapper>(
+  auto identity_manager = std::make_unique<IdentityManagerWrapper>(
       ios::ChromeBrowserState::FromBrowserState(browser_state));
+
+  for (auto& observer : observer_list_)
+    observer.IdentityManagerCreated(identity_manager.get());
+
+  return identity_manager;
+}
+
+void IdentityManagerFactory::BrowserStateShutdown(web::BrowserState* context) {
+  auto* identity_manager = static_cast<IdentityManagerWrapper*>(
+      GetServiceForBrowserState(context, false));
+  if (identity_manager) {
+    for (auto& observer : observer_list_)
+      observer.IdentityManagerShutdown(identity_manager);
+  }
+  BrowserStateKeyedServiceFactory::BrowserStateShutdown(context);
 }

ios/chrome/browser/signin/identity_manager_factory.h

@@ -7,8 +7,11 @@
 
 #include "base/macros.h"
 #include "base/no_destructor.h"
+#include "base/observer_list.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
 
+class IdentityManagerFactoryObserver;
+
 namespace identity {
 class IdentityManager;
 }
@@ -29,15 +32,25 @@ class IdentityManagerFactory : public BrowserStateKeyedServiceFactory {
   // Returns an instance of the IdentityManagerFactory singleton.
   static IdentityManagerFactory* GetInstance();
 
+  // Methods to register or remove observers of IdentityManager
+  // creation/shutdown.
+  void AddObserver(IdentityManagerFactoryObserver* observer);
+  void RemoveObserver(IdentityManagerFactoryObserver* observer);
+
  private:
   friend class base::NoDestructor<IdentityManagerFactory>;
 
   IdentityManagerFactory();
   ~IdentityManagerFactory() override;
 
+  // List of observers. Checks that list is empty on destruction.
+  mutable base::ObserverList<IdentityManagerFactoryObserver, true>::Unchecked
+      observer_list_;
+
   // BrowserStateKeyedServiceFactory:
   std::unique_ptr<KeyedService> BuildServiceInstanceFor(
       web::BrowserState* browser_state) const override;
+  void BrowserStateShutdown(web::BrowserState* context) override;
 
   DISALLOW_COPY_AND_ASSIGN(IdentityManagerFactory);
 };

ios/chrome/browser/signin/identity_manager_factory_observer.h

+// Copyright 2019 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 IOS_CHROME_BROWSER_SIGNIN_IDENTITY_MANAGER_FACTORY_OBSERVER_H_
+#define IOS_CHROME_BROWSER_SIGNIN_IDENTITY_MANAGER_FACTORY_OBSERVER_H_
+
+#include "base/macros.h"
+
+namespace identity {
+class IdentityManager;
+}
+
+// Observer for IdentityManagerFactory.
+class IdentityManagerFactoryObserver {
+ public:
+  IdentityManagerFactoryObserver() {}
+  virtual ~IdentityManagerFactoryObserver() {}
+
+  // Called when an IdentityManager instance is created.
+  virtual void IdentityManagerCreated(identity::IdentityManager* manager) {}
+
+  // Called when a IdentityManager instance is being shut down. Observers
+  // of |manager| should remove themselves at this point.
+  virtual void IdentityManagerShutdown(identity::IdentityManager* manager) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(IdentityManagerFactoryObserver);
+};
+
+#endif  // IOS_CHROME_BROWSER_SIGNIN_IDENTITY_MANAGER_FACTORY_OBSERVER_H_