IndexedDB: Ensure transactions without requests commit in the same order

content/browser/indexed_db/indexed_db_transaction.cc

Index: content/browser/indexed_db/indexed_db_transaction.cc
diff --git a/content/browser/indexed_db/indexed_db_transaction.cc b/content/browser/indexed_db/indexed_db_transaction.cc
index a7f17b6178c24bf5c0675393ed399c392177d648..768cf1dc2f8a96929a372b0659c6a882821619f5 100644
--- a/content/browser/indexed_db/indexed_db_transaction.cc
+++ b/content/browser/indexed_db/indexed_db_transaction.cc
@@ -21,8 +21,19 @@
 
 namespace content {
 
+namespace {
+
 const int64_t kInactivityTimeoutPeriodSeconds = 60;
 
+// Helper for posting a task to call IndexedDBTransaction::Commit when we know
+// the transaction had no requests and therefore the commit must succeed.
+void CommitUnused(scoped_refptr<IndexedDBTransaction> transaction) {
+  leveldb::Status status = transaction->Commit();
+  DCHECK(status.ok());
+}
+
+}  // namespace
+
 IndexedDBTransaction::TaskQueue::TaskQueue() {}
 IndexedDBTransaction::TaskQueue::~TaskQueue() { clear(); }
 
@@ -204,8 +215,16 @@ void IndexedDBTransaction::Start() {
   state_ = STARTED;
   diagnostics_.start_time = base::Time::Now();
 
-  if (!used_)
+  if (!used_) {
+    if (commit_pending_) {
+      // The transaction has never had requests issued against it, but the
+      // front-end previously requested a commit; do the commit now, but not
+      // re-entrantly as that may renter the coordinator.
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE, base::Bind(&CommitUnused, make_scoped_refptr(this)));
+    }
     return;
+  }
 
   RunTasksIfStarted();
 }
@@ -253,6 +272,12 @@ leveldb::Status IndexedDBTransaction::Commit() {
   DCHECK(!used_ || state_ == STARTED);
   commit_pending_ = true;
 
+  // Front-end has requested a commit, but this transaction is blocked by
+  // other transactions. The commit will be initiated when the transaction
+  // coordinator unblocks this transaction.
+  if (state_ != STARTED)
+    return leveldb::Status::OK();
+
   // Front-end has requested a commit, but there may be tasks like
   // create_index which are considered synchronous by the front-end
   // but are processed asynchronously.