[Sync] Add support for enabling session sync remotely.

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..dea6522a7e7d335ae5fba1c6e900e794eb6764ef 100644
--- a/chrome/browser/sync/internal_api/sync_manager.cc
+++ b/chrome/browser/sync/internal_api/sync_manager.cc
@@ -1968,10 +1968,25 @@ void SyncManager::RefreshEncryption() {
 }
 
 syncable::ModelTypeSet SyncManager::GetEncryptedDataTypes() const {
-  sync_api::ReadTransaction trans(FROM_HERE, GetUserShare());
+  ReadTransaction trans(FROM_HERE, GetUserShare());
   return GetEncryptedTypes(&trans);
 }
 
+bool SyncManager::ReceivedExperimentalTypes(syncable::ModelTypeSet* to_add)
+    const {
+  ReadTransaction trans(FROM_HERE, GetUserShare());
+  ReadNode node(&trans);
+  if (!node.InitByTagLookup(kNigoriTag)) {
+    VLOG(1) << "Couldn't find Nigori node.";
+    return false;
+  }
+  if (node.GetNigoriSpecifics().sync_tabs()) {
+    to_add->insert(syncable::SESSIONS);
+    return true;
+  }
+  return false;
+}
+
 bool SyncManager::HasUnsyncedItems() const {
   sync_api::ReadTransaction trans(FROM_HERE, GetUserShare());
   return (trans.GetWrappedTrans()->directory()->unsynced_entity_count() != 0);