[sync] skeleton implementation of TypedURLSyncBridge

chrome/browser/sync/chrome_sync_client.cc

Index: chrome/browser/sync/chrome_sync_client.cc
diff --git a/chrome/browser/sync/chrome_sync_client.cc b/chrome/browser/sync/chrome_sync_client.cc
index 6430bae7499269e01c5e26fc87ff9d39fe0f11d2..88908d1fd76a697e329ed140733f5f8377fb724f 100644
--- a/chrome/browser/sync/chrome_sync_client.cc
+++ b/chrome/browser/sync/chrome_sync_client.cc
@@ -496,6 +496,13 @@ ChromeSyncClient::GetSyncBridgeForModelType(syncer::ModelType type) {
           ->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>();