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

components/precache/content/precache_manager.cc

 // Copyright 2013 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.
 
 #include "components/precache/content/precache_manager.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 105 matching lines @@
       kPrecacheFieldTrialName, kDataReductionProxyParam).empty();
   if (disable_if_proxy &&
       (!data_reduction_proxy_settings_ ||
        data_reduction_proxy_settings_->IsDataReductionProxyEnabled()))
     return AllowedType::DISALLOWED;
 
   if (!(sync_service_ && sync_service_->IsEngineInitialized()))
     return AllowedType::PENDING;
 
   // SyncService delegates to SyncPrefs, which must be called on the UI thread.
-  if (history_service_ &&
+  if (history_service_ && !sync_service_->IsLocalSyncEnabled() &&
       sync_service_->GetActiveDataTypes().Has(syncer::SESSIONS) &&
-      !sync_service_->GetEncryptedDataTypes().Has(syncer::SESSIONS))
+      !sync_service_->GetEncryptedDataTypes().Has(syncer::SESSIONS)) {
     return AllowedType::ALLOWED;
+  }
 
   return AllowedType::DISALLOWED;
 }
 
 void PrecacheManager::OnCacheBackendReceived(int net_error_code) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (net_error_code != net::OK) {
     // Assume there is no cache.
     cache_backend_ = nullptr;
     OnCacheSizeReceived(0);
@@ skipping 341 matching lines @@
       this));
   precache_fetcher_->Start();
 }
 
 void PrecacheManager::OnHostsReceivedThenDone(
     const history::TopHostsList& host_counts) {
   OnDone();
 }
 
 }  // namespace precache