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

components/sync/driver/sync_service.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_SYNC_DRIVER_SYNC_SERVICE_H_
 #define COMPONENTS_SYNC_DRIVER_SYNC_SERVICE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 90 matching lines @@
   // overrides, and account-level overrides are examples of reasons this
   // might be false.
   virtual bool IsSyncAllowed() const = 0;
 
   // Returns true if sync is fully initialized and active. This implies that
   // an initial configuration has successfully completed, although there may
   // be datatype specific, auth, or other transient errors. To see which
   // datetypes are actually syncing, see GetActiveTypes() below.
   virtual bool IsSyncActive() const = 0;
 
+  // Returns true if the local sync backend server has been enabled through a
+  // command line flag or policy. In this case sync is considered active but any
+  // implied consent for further related services e.g. Suggestions, Web History
+  // etc. is considered not granted.
+  virtual bool IsLocalSyncEnabled() const = 0;
+
   // Triggers a GetUpdates call for the specified |types|, pulling any new data
   // from the sync server.
   virtual void TriggerRefresh(const ModelTypeSet& types) = 0;
 
   // Get the set of current active data types (those chosen or configured by
   // the user which have not also encountered a runtime error).
   // Note that if the Sync engine is in the middle of a configuration, this
   // will the the empty set. Once the configuration completes the set will
   // be updated.
   virtual ModelTypeSet GetActiveDataTypes() const = 0;
@@ skipping 205 matching lines @@
  protected:
   SyncService() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SyncService);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_SYNC_SERVICE_H_