IndexedDB: Defer delete calls when there is a running upgrade

content/browser/indexed_db/indexed_db_database.h

Index: content/browser/indexed_db/indexed_db_database.h
diff --git a/content/browser/indexed_db/indexed_db_database.h b/content/browser/indexed_db/indexed_db_database.h
index 72d65ce723e985a331cdd2c3e286af32d2ade7c3..fd03086664a3560f415e5cc9031d20ea332643f9 100644
--- a/content/browser/indexed_db/indexed_db_database.h
+++ b/content/browser/indexed_db/indexed_db_database.h
@@ -264,6 +264,9 @@ class CONTENT_EXPORT IndexedDBDatabase
   typedef std::list<PendingDeleteCall*> PendingDeleteCallList;
   typedef list_set<IndexedDBConnection*> ConnectionSet;
 
+  bool IsUpgradeRunning() const;
+  bool IsUpgradePendingOrRunning() const;
+
   bool IsOpenConnectionBlocked() const;
   leveldb::Status OpenInternal();
   void RunVersionChangeTransaction(
@@ -304,12 +307,39 @@ class CONTENT_EXPORT IndexedDBDatabase
   IndexedDBTransactionCoordinator transaction_coordinator_;
 
   TransactionMap transactions_;
+
+  // An open request ends up here if:
+  //  * There is a running or pending upgrade.
+  //  * There are pending deletes.
+  // Requests here have *not* broadcast OnVersionChange if necessary.
+  // When no longer blocked, the OpenConnection() calls are remade.
   PendingOpenCallList pending_open_calls_;
+
+  // This owns the connection for the first upgrade request (open with higher
+  // version) that could not be immediately processed. The request has already
+  // broadcast OnVersionChange if necessary.
   std::unique_ptr<PendingUpgradeCall>
       pending_run_version_change_transaction_call_;
+
+  // This references a connection for an upgrade request while the upgrade
+  // transaction is running, so that the success/error result can be sent. It
+  // is not set until the upgrade transaction actually starts executing
+  // operations, so do not rely on it to determine if an upgrade is in
+  // progress.
   std::unique_ptr<PendingSuccessCall> pending_second_half_open_;
+
+  // A delete request ends up here if:
+  //  * There is a running upgrade.
+  // Requests here have *not* broadcast OnVersionChange if necessary.
+  // When no longer blocked, DeleteDatabase() calls are remade.
   PendingDeleteCallList pending_delete_calls_;
 
+  // A delete request ends up here if:
+  //  * There are open connections.
+  // Requests here have already broadcast OnVersionChange if necessary.
+  // When no longer blocked, DeleteDatabaseFinal() calls are made.
+  PendingDeleteCallList blocked_delete_calls_;
+
   ConnectionSet connections_;
   bool experimental_web_platform_features_enabled_;