sync: make ServerConnectionManager explicitly NonThreadSafe

chrome/browser/sync/internal_api/sync_manager.cc

Index: chrome/browser/sync/internal_api/sync_manager.cc
diff --git a/chrome/browser/sync/internal_api/sync_manager.cc b/chrome/browser/sync/internal_api/sync_manager.cc
index c0b9cb35ff7e9c075139b36b90fff849a036970b..9704c5071b208139a60458d530055778fe2c6c78 100644
--- a/chrome/browser/sync/internal_api/sync_manager.cc
+++ b/chrome/browser/sync/internal_api/sync_manager.cc
@@ -1281,6 +1281,7 @@ void SyncManager::SyncInternal::OnIPAddressChanged() {
 }
 
 void SyncManager::SyncInternal::OnIPAddressChangedImpl() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   // TODO(akalin): CheckServerReachable() can block, which may cause
   // jank if we try to shut down sync.  Fix this.
   connection_manager()->CheckServerReachable();
@@ -1288,6 +1289,7 @@ void SyncManager::SyncInternal::OnIPAddressChangedImpl() {
 
 void SyncManager::SyncInternal::OnServerConnectionEvent(
     const ServerConnectionEvent& event) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   allstatus_.HandleServerConnectionEvent(event);
   if (event.connection_code ==
       browser_sync::HttpResponse::SERVER_CONNECTION_OK) {