IndexedDB: Ignore duplicate transaction IDs sent by renderer

content/browser/indexed_db/indexed_db_database.cc

Index: content/browser/indexed_db/indexed_db_database.cc
diff --git a/content/browser/indexed_db/indexed_db_database.cc b/content/browser/indexed_db/indexed_db_database.cc
index f0c05a58015a54de9491fcb274da8660fa8a6604..7980be511d352098c7de37fbd961c526796a8493 100644
--- a/content/browser/indexed_db/indexed_db_database.cc
+++ b/content/browser/indexed_db/indexed_db_database.cc
@@ -1398,6 +1398,9 @@ void IndexedDBDatabase::CreateTransaction(
     uint16 mode) {
 
   DCHECK(connections_.has(connection));
+  DCHECK(transactions_.find(transaction_id) == transactions_.end());
+  if (transactions_.find(transaction_id) != transactions_.end())
+    return;
 
   scoped_refptr<IndexedDBTransaction> transaction = new IndexedDBTransaction(
       transaction_id,
@@ -1405,7 +1408,6 @@ void IndexedDBDatabase::CreateTransaction(
       std::set<int64>(object_store_ids.begin(), object_store_ids.end()),
       static_cast<indexed_db::TransactionMode>(mode),
       this);
-  DCHECK(transactions_.find(transaction_id) == transactions_.end());
   transactions_[transaction_id] = transaction;
 }