[sync] skeleton implementation of TypedURLSyncBridge

chrome/browser/sync/chrome_sync_client.cc

 // 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.
 
 #include "chrome/browser/sync/chrome_sync_client.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 478 matching lines @@
       return base::WeakPtr<syncer::ModelTypeSyncBridge>();
     case syncer::AUTOFILL:
       return autofill::AutocompleteSyncBridge::FromWebDataService(
           web_data_service_.get());
 #if defined(OS_CHROMEOS)
     case syncer::PRINTERS:
       return chromeos::PrintersManagerFactory::GetForBrowserContext(profile_)
           ->GetSyncBridge()
           ->AsWeakPtr();
 #endif
+    case syncer::TYPED_URLS: {
+      history::HistoryService* history = HistoryServiceFactory::GetForProfile(

[skym, 2017/03/07 18:08:04]

So, every other place we access the HistoryService in this file uses
EXPLICIT_ACCESS. It is odd at this place is different. My understanding is that
we haven't gotten to the bottom of how this should work.

I'd prefer you to add a TODO and just return an empty weak ptr until we get to
the bottom of this, similar to what you did in
profile_sync_components_factory_impl.cc

[Gang Wu, 2017/03/31 19:35:58]

Done.

+          profile_, ServiceAccessType::IMPLICIT_ACCESS);
+      if (!history)
+        return base::WeakPtr<history::TypedURLSyncBridge>();
+      return history->GetTypedURLSyncBridge()->AsWeakPtr();
+    }
     default:
       NOTREACHED();
       return base::WeakPtr<syncer::ModelTypeSyncBridge>();
   }
 }
 
 scoped_refptr<syncer::ModelSafeWorker>
 ChromeSyncClient::CreateModelWorkerForGroup(syncer::ModelSafeGroup group) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   switch (group) {
@@ skipping 183 matching lines @@
   sync_service->RegisterDataTypeController(
       base::MakeUnique<SupervisedUserSyncDataTypeController>(
           syncer::SUPERVISED_USER_SETTINGS, error_callback, this, profile_));
   sync_service->RegisterDataTypeController(
       base::MakeUnique<SupervisedUserSyncDataTypeController>(
           syncer::SUPERVISED_USER_WHITELISTS, error_callback, this, profile_));
 #endif
 }
 
 }  // namespace browser_sync