[Sync] Allow sync start without sign-in if the local sync backend is on.

components/sync/engine_impl/sync_scheduler_impl.h

Index: components/sync/engine_impl/sync_scheduler_impl.h
diff --git a/components/sync/engine_impl/sync_scheduler_impl.h b/components/sync/engine_impl/sync_scheduler_impl.h
index b91c1cbe1fc1417903e020d5b328d1c829264a2a..b27ca4a23bc6a29c81ac503a65537f21c47aea7d 100644
--- a/components/sync/engine_impl/sync_scheduler_impl.h
+++ b/components/sync/engine_impl/sync_scheduler_impl.h
@@ -41,7 +41,8 @@ class SyncSchedulerImpl : public SyncScheduler, public base::NonThreadSafe {
   SyncSchedulerImpl(const std::string& name,
                     BackoffDelayProvider* delay_provider,
                     SyncCycleContext* context,
-                    Syncer* syncer);
+                    Syncer* syncer,
+                    bool local_sync_backend_enabled);

[Nicolas Zea, 2016/12/15 00:37:28]

nit: how about renaming this to ignore_auth_credentials or something like that,
to make it more clear what behavior this is controlling. It seems like a
layering violation to be exposing the backend state here.

This also applies to SyncManager and the other layers below PSS that don't
really care what kind of backend there is.

[pastarmovj, 2016/12/16 17:04:48]

Done.

 
   // Calls Stop().
   ~SyncSchedulerImpl() override;
@@ -292,6 +293,10 @@ class SyncSchedulerImpl : public SyncScheduler, public base::NonThreadSafe {
   // One-shot timer for scheduling GU retry according to delay set by server.
   base::OneShotTimer retry_timer_;
 
+  // Whether the local file based sync backend should be enabled. Dictates if
+  // the sheduler should wait for authentication to happen or not.
+  bool local_sync_backend_enabled_;
+
   base::WeakPtrFactory<SyncSchedulerImpl> weak_ptr_factory_;
 
   // A second factory specially for weak_handle_this_, to allow the handle