Add Observer to //chrome's IdentityManagerFactory

IdentityManagerFactory::Observer is a parallel interface to//chrome's
SigninManagerFactory::Observer. It will be used to replace usage of
that observer in follow up CLs.

BUG=927341

Change-Id: Id377b5b5e20e00b49811302b0ab26a611af1d3d4
Reviewed-on: https://chromium-review.googlesource.com/c/1448754
Auto-Submit: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#628316}

chrome/browser/signin/identity_manager_factory.cc

@@ -123,7 +123,30 @@ IdentityManagerFactory::BuildAuthenticatedServiceInstanceForTesting(
   return identity_manager;
 }
 
+void IdentityManagerFactory::AddObserver(Observer* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void IdentityManagerFactory::RemoveObserver(Observer* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
 KeyedService* IdentityManagerFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
-  return new IdentityManagerWrapper(Profile::FromBrowserContext(context));
+  auto identity_manager = std::make_unique<IdentityManagerWrapper>(
+      Profile::FromBrowserContext(context));
+  for (Observer& observer : observer_list_)
+    observer.IdentityManagerCreated(identity_manager.get());
+  return identity_manager.release();
+}
+
+void IdentityManagerFactory::BrowserContextShutdown(
+    content::BrowserContext* context) {
+  auto* identity_manager = static_cast<IdentityManagerWrapper*>(
+      GetServiceForBrowserContext(context, false));
+  if (identity_manager) {
+    for (Observer& observer : observer_list_)
+      observer.IdentityManagerShutdown(identity_manager);
+  }
+  BrowserContextKeyedServiceFactory::BrowserContextShutdown(context);
 }

chrome/browser/signin/identity_manager_factory.h

@@ -9,6 +9,7 @@
 #include <string>
 
 #include "base/memory/singleton.h"
+#include "base/observer_list.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 namespace identity {
@@ -21,6 +22,21 @@ class Profile;
 // Profiles.
 class IdentityManagerFactory : public BrowserContextKeyedServiceFactory {
  public:
+  class Observer {
+   public:
+    // Called when a IdentityManager instance is created.
+    virtual void IdentityManagerCreated(
+        identity::IdentityManager* identity_manager) {}
+
+    // Called when a IdentityManager instance is being shut down. Observers
+    // of |identity_manager| should remove themselves at this point.
+    virtual void IdentityManagerShutdown(
+        identity::IdentityManager* identity_manager) {}
+
+   protected:
+    virtual ~Observer() {}
+  };
+
   static identity::IdentityManager* GetForProfile(Profile* profile);
   static identity::IdentityManager* GetForProfileIfExists(
       const Profile* profile);
@@ -37,6 +53,11 @@ class IdentityManagerFactory : public BrowserContextKeyedServiceFactory {
                                               const std::string& refresh_token,
                                               content::BrowserContext* context);
 
+  // Methods to register or remove observers of IdentityManager
+  // creation/shutdown.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
  private:
   friend struct base::DefaultSingletonTraits<IdentityManagerFactory>;
 
@@ -46,6 +67,10 @@ class IdentityManagerFactory : public BrowserContextKeyedServiceFactory {
   // BrowserContextKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* profile) const override;
+  void BrowserContextShutdown(content::BrowserContext* profile) override;
+
+  // List of observers. Checks that list is empty on destruction.
+  mutable base::ObserverList<Observer, true>::Unchecked observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(IdentityManagerFactory);
 };