[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 295fdfb8744f2e644e06eb11f0344dbc64232807..a7fa143973cc1624f35376e1eefa465af2111b26 100644
--- a/chrome/browser/sync/chrome_sync_client.cc
+++ b/chrome/browser/sync/chrome_sync_client.cc
@@ -456,6 +456,17 @@ ChromeSyncClient::GetSyncBridgeForModelType(syncer::ModelType type) {
           ->GetSyncBridge()
           ->AsWeakPtr();
 #endif
+    case syncer::TYPED_URLS: {
+      // We request history service with explicit access here because this
+      // codepath is executed on backend thread while HistoryServiceFactory

[skym, 2017/03/03 17:41:09]

I'm not sure I agree with you that the way the code is currently set up in this
CL, will actually call this on anything other than the UI thread.

[Gang Wu, 2017/03/06 08:21:23]

Done.

+      // checks preference value in implicit mode and PrefService expectes calls
+      // only from UI thread.
+      history::HistoryService* history = HistoryServiceFactory::GetForProfile(
+          profile_, ServiceAccessType::EXPLICIT_ACCESS);
+      if (!history)
+        return base::WeakPtr<history::TypedURLSyncBridge>();
+      return history->GetTypedURLSyncBridge()->AsWeakPtr();
+    }
     default:
       NOTREACHED();
       return base::WeakPtr<syncer::ModelTypeSyncBridge>();