Introduce Identity Service and its initial usage

chrome/browser/profiles/profile_impl.h

Index: chrome/browser/profiles/profile_impl.h
diff --git a/chrome/browser/profiles/profile_impl.h b/chrome/browser/profiles/profile_impl.h
index 56f8b580c4e91842e53a407a250b96339b95d9c9..54093b9ce0309d2847af68e2365c746b9afa8582 100644
--- a/chrome/browser/profiles/profile_impl.h
+++ b/chrome/browser/profiles/profile_impl.h
@@ -196,6 +196,10 @@ class ProfileImpl : public Profile {
   std::unique_ptr<domain_reliability::DomainReliabilityMonitor>
   CreateDomainReliabilityMonitor(PrefService* local_state);
 
+  // Creates an instance of the Identity Service for this Profile, populating it
+  // with the appropriate instances of its dependencies.
+  std::unique_ptr<service_manager::Service> CreateIdentityService();

[msarda, 2017/03/23 10:48:57]

Is it the goal to add the services as part of the Profile object. On downside I
can think of is that this will not work on iOS.

[blundell, 2017/03/24 09:37:59]

It's neither a goal nor a non-goal, but is a tool that can be used when
necessary. In this case it's necessary because the Identity Service needs to be
passed per-Profile classes on its creation. When bringing up services on iOS,
we'll add a corresponding mechanism to attach service creation to
ChromeBrowserState.

In the long term, the Identity Service will be able to instantiate the classes
that it needs internally, because there won't be any other direct consumers of
those classes. Once we've reached that point (which is far down the road
obviously), the Identity Service won't need to be created by the Profile
anymore.

+
   PrefChangeRegistrar pref_change_registrar_;
 
   base::FilePath path_;