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

components/browser_sync/profile_sync_service.h

Index: components/browser_sync/profile_sync_service.h
diff --git a/components/browser_sync/profile_sync_service.h b/components/browser_sync/profile_sync_service.h
index 9ef6d1869fc911b5a23c440cba5357ffb8065414..f3183f4d852ef5ed560e081fc4feb9e7d07fbcf6 100644
--- a/components/browser_sync/profile_sync_service.h
+++ b/components/browser_sync/profile_sync_service.h
@@ -246,6 +246,8 @@ class ProfileSyncService : public syncer::SyncService,
     std::string debug_identifier;
     version_info::Channel channel = version_info::Channel::UNKNOWN;
     base::SequencedWorkerPool* blocking_pool = nullptr;
+    bool local_sync_backend_enabled = false;
+    base::FilePath local_sync_backend_folder;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(InitParams);
@@ -849,6 +851,12 @@ class ProfileSyncService : public syncer::SyncService,
   // backend to refresh its credentials.
   bool is_auth_in_progress_;
 
+  // Set to true when sync should use a local sync backend to store its data.
+  bool local_sync_backend_enabled_;
+
+  // The location where the local sync backend stores its data.
+  base::FilePath local_sync_backend_folder_;
+
   // Encapsulates user signin - used to set/get the user's authenticated
   // email address.
   const std::unique_ptr<SigninManagerWrapper> signin_;